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NCR-days 2011: Controlling the Dutch Rivers
Book of Abstracts
Delft, October 27-28th, 2011
Delft University of Technology
Nederlands Centrum voor Rivierkunde
NCR – the Netherlands Centre for River Research – is a cooperation of the Universities
of Delft, Utrecht, Nijmegen, Twente and Wageningen, UNESCO-IHE, RWS-WD, ALTERRA
and Deltares
The NCR days 2011 are supported financially by the Netherlands Foundation for
Scientific Research (NWO), Division Earth and Life Sciences.
1
NCR-days 2011: Controlling the Dutch Rivers
Book of Abstracts
2
NCR-days 2011 Conference venue
Delft University of Technology
Building 23 (Civil Engineering) room E
Stevinweg 1
2628CN Delft
(http://home.tudelft.nl/over-tu-delft/contact-en-bereikbaarheid)
Contact address NCR-Deltares
Ms. Jolien Mans Donker
Deltares
Programme secretariat CRK
Postbus 177
2600 MH Delft
T +31 (0) 88 335 8557
W www.deltares.nl
W www.nck-web.deltares.nl
W www.ncr-web.deltares.nl
Contact address NCR-Days 2011 Program and Abstracts
Erik Mostert
Dept. Water Resources Management
Faculty of Civil Engineering, Delft University of Technology
Stevinweg 1
2628CN Delft
T +31 (0)15 27 87800
3
Table of contents
Preface 6
Program 7
List of poster presentations 9
Abstracts 10
S. Ali et al. Numerical and physical modelling of rapidly varying flow
over weir-like obstacles in rivers and floodplains
11
B. Biazin et al. Tied-ridges for water conservation in the Rift Valley
Drylands of Ethiopia
13
B. Blossier et al. Impact of shipping on the Waal River water level
14
M.P.Boersema Physical scale model with a mobile bed composed
of lightweight sediment
to establish morphodynamic behaviour around a training
dam (River Rhine - The Netherlands)
15
W.M. van Dijk et al. Experimental rivers: from braided towards meandering by
the addition of cohesive floodplain material
17
F.A. Elizondo García et
al.
Do invasive benthic mollucs impact river morphology?
18
G. Ermers et al. Quantifying vegetation succession in floodplains using map
series
20
E. Facchini et al. Morphological aspects of cyclic rejuvenation of the section
scale
21
H. Havinga Self Supporting River System to reduce maintenance
23
H. Hidayat Discharge estimation in a backwater affected meandering
river
24
L. van Kouwen et al. Exploring the ecological benefits of water level
management in impounded rivers: case study River
Meuse (the Netherlands)
25
B. Makaske et al. The influence of floodplain vegetation succession on
hydraulic roughness: is nature restoration in Dutch
embanked floodplains compatible with flooding safety
standards?
27
4
H. Mianabadi et al. Hydropolitics of Hirmand river, water dispute between
Iran and Afghanistan
28
M. M. de Molenaar et al. Reconstructing palaeo peak flow regimes for the river
Rhine
29
A. Montes Arboleda et
al.
Reconstruction of the early 19th century Waal River
31
W. Ottevanger et al. Parameterization of bank shear stresses in curved open
channel flow based on large-eddy simulations
32
D.R. Van Putten et al. 2D-morphological modelling of side channels
33
S. Quartel et al. Dynamic stage-discharge relations of the Dutch Rhine
branches
35
L. Raso et al. Optimal anticipatory control of river structures using
Ensemble Forecasting System
37
M.G. Sassi et al. Suspended sediment discharge distribution at tidally
affected river bifurcations
38
M.M. Schoor et al. Future longitudinal dams in the Dutch Rhine
39
F. Schuurman et al. Self-formed braid bars in a numerical model
40
S. Segni Abawallo et al. Performance off-line detention basins to inlet structure
design
41
R. van der Sligte Questions from the Dutch Delta: Morphological modeling of
the tidal river
42
N. Slootjes et al. Options for adaptation to climate change for the Rhine
Meuse Delta
44
E. Stouthamer et al. Substrate geology affecting local erodibilty in the bed of the
River Lek
(Rhine delta, The Netherlands)
46
M. Straatsma et al. Uncertainty in bio-geomorphological assessments of
lowland river floodplains resulting from landcover
classification errors
48
J. Talsma A New suit for the IJsselmeer
Possibilities for facing the future needs of the lake by
means of an optimized dynamic target water level
50
Trang Van Pham
Tracking the uncertainty in streamflow prediction through
a hydrological forecasting system
52
B. Vermeulen et al. Measuring profiles of turbulence quantities with two
coupled ADCPs in geophysical surface flows
54
5
M. Vierstra Real-time control of a water system the size of Holland
(Jiangsu, China)
55
Wei Li et al. Numerical investigation for characteristics of
hyperconcentrated flood propagation
56
N. Wijermans et al. Dynamic modeling: social and physical interactions to
explore future water management
57
M. Zethof Risk-based control of external salt water intrusion for the
Rhine-Meuse Estuary
59
Zheng Bing Wang Effects of discharge fluctuation on morphological
equilibrium of rivers
61
6
Preface
The Netherlands Centre for River Studies (NCR) aims to provide an open platform for all
people interested in scientific research and communication on river issues. One of its
activities is to organize the NCR-Days once a year. On two consecutive days scientists present
their ongoing river studies, in order to maximize the exchange of ideas and experiences
between the participants and to provide the researchers a podium for their study approach
and preliminary results. Based on these contacts, they can improve their approach and
possibly establish additional co-operation.
The title of the NCR-days 2011 is "Controlling the Dutch rivers". The Dutch rivers fulfill many
different functions. To manage the national flows and water levels, adjustable infrastructure,
such as weirs, sluices and pumping stations exist. At the NCR days, possibilities for making
more use of this existing infrastructure will be explored, using for instance real-time
monitoring and meteorological predictions. In addition, there was room for other
presentations in the field of hydrology, morphology, ecology and river management.
The NCR-Days 2011 have been organized by a small committee consisting of the undersigned
and Gertjan Geerling (Deltares, programme secretary NCR), in cooperation with Hanneke de
Jong (secretariat Department of Water Management, Delft University of Technology) and
Jolien Mans (secretariat NCR). We would like to thank all others who have already or will
contribute to the organization of these days!
On behalf of the organizing committee,
Delft, October 2010
Erik Mostert
Delft University of Technology
7
Program
Day 1, 27th of October 2011
09.30-10.00 Registration
10.00-10.15 Opening
10.15-11.00 Keynote 1: Challenges of Dutch river management (M. van der Vlist,
Rijkswaterstaat Waterdienst)
11.00-11.30 Coffee
11.30-12.30 Session 1: Hydrology
• S. Quartel, et al.: Dynamic stage-discharge relations of the Dutch Rhine
branches
• H. Hidayat et al.: Discharge estimation in a backwater affected
meandering river
• M.M. de Molenaar et al.: Reconstructing palæo peak flow regimes for the
river Rhine
12.30-13.30 Lunch
13.30-15.00 Session 2: Morphology
• R. van der Sligte: Questions from the Dutch Delta; Morphological
modeling of the tidal river
• A. Montes Arboleda et al.: Reconstruction of the early 19th century Waal
river
• D.R. Van Putten et al.: 2D-morphological modelling of side channels
• H.J. Pierik et al.: Substrate geology affecting local erodibilty in the bed of
the River Lek (Rhine delta, The Netherlands)
15.00-15.30 Tea
15.30-17.00 Session 3: River basin management
• H. Havinga: Self Supporting River System to reduce maintenance
• M.P. Boersema: Physical scale model with a mobile bed composed of
lightweight sediment to establish morphodynamic behaviour around a
training dam (River Rhine - The Netherlands).
• B. Makaske et al.: The influence of floodplain vegetation succession on
hydraulic roughness: is nature restoration in Dutch embanked floodplains
compatible with flooding safety standards?
• N. Wijermans et al.: Dynamic modeling: social and physical interactions to
explore future water management
18.30-19.00 Drinks
19.00-22.00 Dinner
8
Day 2, 28th of October 2011
09.00-10.00 Keynote 2: Managing infrastructure (P.-O. Malaterre, CEMAGREF, Montpellier,
France)
10.00-10.30 Coffee
10.30-12.00 Session 4: Highlights on infrastructure management
• L. Raso at al.: Optimal anticipatory control of river structures using
Ensemble Forecasting System
• M. Vierstra: Real-time control of a water system the size of Holland
(Jiangsu, China)
• M. Zethof: Risk-based control of external salt water intrusion for the
Rhine-Meuse Estuary
• L. van Kouwen et al.: Exploring the ecological benefits of water level
management in impounded rivers: case study River Meuse (the
Netherlands)
12.00-12.30 Elevator pitches posters
12.30-13.30 Lunch
13.30-14.30 Poster session, time for side meetings
14.00-16.00 Innovating Dutch River management; Panel discussion
N.C. van de Giesen (TU Delft and Topteam Water), G. J. Akkerman (Royal
Haskoning), T. Buijse (Deltares) and H. Havinga (Rijkswaterstaat)
16.00-16.30 Wrap up session, final discussion, awards best paper and best poster
16.30-17.30 Drinks
9
List of poster presentations
• S. Ali et al.: Numerical and physical modelling of rapidly varying flow over weir-like
obstacles in rivers and floodplains
• B. Biazin et al.: Tied-ridges for water conservation in the Rift Valley Drylands of Ethiopia
• B. Blossier et al.: Impact of shipping on the Waal River water level
• W.M. van Dijk et al.: Experimental rivers: from braided towards meandering by the
addition of cohesive floodplain material
• F.A. Elizondo García et al: Do invasive benthic mollucs impact river morphology?
• G. Ermers et al.: Quantifying vegetation succession in floodplains using map series
• E. Facchini et al.: Morphological aspects of cyclic rejuvenation of the section scale
(Ewijkse Plaat) and reach scale of the Waal River, the Netherlands
• H. Mianabadi: Hydropolitics of Hirmand river, water dispute between Iran and
Afghanistan
• W. Ottevanger et al.: Parameterization of bank shear stresses in curved open channel
flow based on large-eddy simulations
• M.G. Sassi et al.: Suspended sediment discharge distribution at tidally affected river
bifurcations
• M. Schoor et al.: Future longitudinal dams in the Dutch Rhine
• F. Schuurman et al.: Self-formed braid bars in a numerical model
• S. Segni Abawallo et al.: Performance Off-Line Detention Basins To Inlet Structure Design
• N. Slootjes et al.: Options for adaptation to climate change for the Rhine Meuse Delta
• M. Straatsma et al.: Uncertainty in bio-geomorphological assessments of lowland river
floodplains resulting from landcover classification errors
• J. Talsma: A New suit for the Ijsselmeer; Possibilities for facing the future needs of the
lake by means of an optimized dynamic target water level
• Trang Van Pham: Tracking the uncertainty in streamflow prediction through a
hydrological forecasting system
• B. Vermeulen et al.: Measuring profiles of turbulence quantities with two coupled ADCPs
in geophysical surface flows
• Wei Li et al.: Numerical investigation for characteristics of hyperconcentrated flood
propagation
• Zheng Bing Wang: Effects of discharge fluctuation on morphological equilibrium of rivers
10
Abstracts
11
Numerical and physical modelling of rapidly varying flow over weir-like
obstacles in rivers and floodplains
S.Ali and W.S.J. Uijttewaal, Environmental Fluid Mechanics Section, Faculty of Civil Engineering
and Geosciences, Delft University of Technology, P.O.Box 5048, 2600GA, Delft, The Netherlands
During high water stages, the flows in the main river channel as well as over groyne fields
and floodplains are complicated. Resistance to flow conveyance is not only caused by the
form and grain drag of the bed but also by many other features such as groynes, vegetation,
dykes and access roads. Some of these features, like summer dykes and groynes, can be
schematised as weirs. These obstacles contribute significantly to the floodplain flow
resistance. An accurate prediction of the flow resistance puts high demands on the computer
modeling. The large dimensions of the river and the capacity of contemporary computers
allow only numerical simulations with a coarse resolution where the details of bathymetry
can not be fully resolved. In current modeling approaches, these effects are captured by
parameterizations with a limited physical basis that require extensive calibration.
The objective of this study is to understand, model and parameterize the form drag caused by
the above mentioned resistive elements in the river and floodplains. Based on this
understanding, the computer models (1D and 2D flow models which could not resolve all
features in the floodplains and rivers) should be improved with respect to correct
representation of hydraulic resistance (physics based) caused by the vegetated dykes.
The flow over such weir-like hydraulic structures is characterized as a rapidly varying free
surface flow. Often these flows are simulated with hydrostatic models which are used in
studying shallow water flows such as rivers, lakes and estuaries. This assumption is valid in
many cases however there are some cases where this is questionable. One example of this is
the undular flow over the obstacles in the flow path. More sophisticated models are required
to simulate such kind of flows and the non-hydrostatic pressure effects are required to be
taken into account.
Many experimental studies have been done to estimate the flow resistance caused by the
weir-like structures, and a variety of empirical relations is available to estimate the discharge
coefficients for weir flows for different regimes. Some studies describe the discharge
coefficient caused by such features during high water stages based on an expansion-loss form
drag model for submerged flow regimes.
An experimental study has been done to determine the energy head losses caused by the
weir-like obstacles and the longitudinal vertical velocity profiles in the flume upstream and
downstream of the schematized models of weir-like obstacles with different shapes and up-,
and downstream slopes. Turbulence intensities, Reynolds averaged shear and normal
stresses and the length of recirculation zone behind such obstacles have been investigated as
well. Finally the characteristics of undular hydraulic jumps behind the obstacles are
determined.
A numerical study of the mentioned flows has been conducted by using 2DV- RANS
mathematical model including free surface modeling. A non-linear k-ε model has been
applied for turbulence closure. The computational results for the velocity profiles and the
free surface profiles have been compared with the measured data. The flow conditions under
which the undulations occur and the wave characteristics of the undular hydraulic jump
caused by the weir-like obstacles have been also investigated by numerical simulations in this
particular study. The non-hydrostatic model is better than hydrostatic model and by means of
12
the non-hydrostatic model the position of hydraulic jump and surface wave can be predicted
fairly well. The non-linear k-ε turbulence model can capture the undulations and
recirculation zone behind the embankment weir properly. Good agreement is found between
numerical (2DV- RANS (non-hydrostatic) and non-linear k-ε model turbulence model) and
experimental results.
13
Tied-ridges for water conservation in the Rift Valley Drylands of Ethiopia
Birhanu Biazinab*, Leo Stroosnijdera, Geert Sterkc
aWageningen University, Land Degradation and Development, P.O.Box 47, 6700 AA
Wageningen, the Netherlands bHawassa University, Wondo Genet College of Forestry and Natural Resources, P.O.Box, 128,
Shashemene, Ethiopia cUtrecht University, Department of Physical Geography, P.O.Box 80115, 3508 TC Utrecht, 12 the
Netherlands
In the predominantly rainfed agricultural system of the sub-Saharan Africa, the agricultural
water scarcity is much linked to the variability of rainfall and excessive non-productive losses
via runoff and evaporation than with the total annual values. The vast Rift Valley drylands of
Ethiopia are characterized by poor sandy loam soils and unreliable, variable rainfall
conditions. A field experiment was done to examine the effect of tied-ridges, sub-soiling and
manure additions in improving the rainwater use efficiency of the smallholder-based maize
farming during a very dry (2009 growing season) and normal (2010 growing season) rainfall
conditions. The long-term effect of tied-ridges on maize yields was simulated using the FAO’s
AquaCrop model. Field results indicated that between 18 and 30% of the rainfall could be lost
in the form of runoff under the traditional tillage system. The soil water status of the root
zone was improved by 10.9% and 3.3% due to the use of tied-ridges and sub-soiling
respectively during a normal rainfall while their effect on a very dry year was negligible.
Overall, a combination dry farmyard manure (4.5 Mg ha-1) and tied-ridges increased the
maize grain yield by 47% as compared to the traditional tillage without manure during a
normal rainfall year. After proper calibration and validation of AquaCrop, long term
simulations revealed that the effect of tied-ridges is better than improving the fertility level of
the soil during below average rainfall seasons. But during high rainfall years, the rainwater
that is conserved through tied-ridges can be effectively utilised only when the fertility level of
the soil is improved. The productive green “transpiration” can be increased by about 34%
when combined application of tied-ridges and optimum soil fertility is used as compared to
the traditional tillage without fertilizer. Hence, the Grain water use efficiency of maize can be
doubled. The future of green revolution in sub-Saharan Africa needs to combine agronomic
measures with rainwater harvesting ideals.
Key words: Tied-ridges, Rift Valley drylands, Rainwater Use Efficiency, Ethiopia
14
Impact of shipping on the Waal River water level
by Blossier B. and van der Wal M., Deltares, Rotterdamseweg 185, Delft, The Netherlands
The Waal River (The Netherlands) is one of the rivers with the highest commercial shipping
intensity among the world. Today the Dutch institutions are implementing the program
‘Room for the River’ in order to limit the risk of flooding in the country. One of the projects of
Room for the River is to lower the groynes along the Waal River. To establish the effects of
groyne lowering, an extensive monitoring program had been undertaken. A part of the
monitoring program is to register the water levels at various stations in the middle Waal. The
efforts are focused on the understanding of the impact of lowered groynes on river water
levels, The role of the navigation on the processes in groyne cells has not yet been clearly
assessed. The present study proposes an analysis of 1 and 2 Hz sampled datasets of water
levels measured in two different groyne fields of the Waal. An additional analysis is
performed on long-term measurements of water levels at six different stations along the Waal
every 10 minutes during several months.
Regarding the high-frequency dataset, in four groyne cells, the deviations of the water level
distributions towards the lowest values reflects the impact of the skewed ship primary waves.
The low frequency variations of the water level (20 minutes to 2 hours oscillation periods)
are compared to the standard deviation of the high frequency range of the signals (ship
waves). In addition, the largest ship waves are located in the signals. Low water levels are
found to coincide with the period of the highest ship waves and the passing of barge-tows
trains.
The variance density spectra of the signals show that the ship primary wave characteristics
depend directly on the shape of the groyne cells. However, one specific groyne cell impacting
locally the primary ship waves does not influence the amplitude of the low frequency water
level oscillations, due to their spatial length much larger than the groyne cell size.
The long-term measurements are presenting a weekly variation in the water level of the river
Waal with a difference reaching 4cm between the highest and lowest water levels. The
hypothesis is made that the rise of the water level during the week is related to the traffic
intensity on the Waal during the weekdays.
The data analysis showed the significant influence of navigation on the water level of the
river Waal. Weekly variations have been observed with higher water levels experienced
during weekdays. Barge-tow trains are also responsible for variations in the water level at
the timescale of a few tens of minutes. The shape of the groyne fields plays a role in the ship
wave height but does not significantly influences the low frequency water level variations.
This study has been performed as a part of a traineeship program of Deltares and Delft
University.
15
Physical scale model with a mobile bed composed of lightweight
sediment to establish morphodynamic behaviour around a training
dam (River Rhine - The Netherlands)
M.P.Boersema1, A.J.F. Hoitink1,2, A. Sieben3, C.J. Sloff4,5and M. van der Wal4
1Hydrology and Quantitative Water Management Group, Department of Environmental Sciences,
Wageningen University, Wageningen, Netherlands 2Institute for Marine and Atmospheric Research Utrecht, Department of Physical Geography,
Faculty of Geosciences, Utrecht University, TC Utrecht, Netherlands 3Rijkswaterstaat, Waterdienst, Lelystad, Netherlands
4Deltares (formerly WL Delft Hydraulics), Delft, Netherlands. 5Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, Netherlands.
Contact details: [email protected]; Droevendaalsesteeg 4, Wageningen 6700 AA, The
Netherlands
To manage the expected extremity in high and low river discharge, the state authority for
infrastructure Rijkswaterstaat in the Netherlands, is searching for an alternative river design.
Currently, the banks on both sides of the River Rhine are protected by groynes. Besides bank
protection, the groynes keep the cross-section of the river relative narrow, to ensure water
depth for navigation. During high water, however, the groynes are flooded and cause an
increase in hydraulic roughness and because of this an increase in water level.
A possibility to ensure the navigation depth during low flow, and reduce the water levels
during a high discharges, is the replacement of the groynes by a training dam at the inner
bend of the river (Figure 1). The training dam will be placed at 30 meter from the head of the
removed groynes and parallel to the river bank. Only at the shallow inner bend there is space
for a new construction without reducing the width of the fairway. Between the training dam
and the bank a new channels is created. The flow into this side channel is regulated by a fixed
weir, so only a limited discharge will flow through the side channel during a low flow
situation. During a flood the large amount of water can discharge trough the side channel,
because extra space is created since the groynes are removed.
An uncertainty in the new dam and weir design is the behaviour of the river bed morphology
during low and high flow. To adequately test the unknown morphological effects at local scale
(dam size scale) a physical scale model is built in a flume (Figure 2). The scale model captures
both the bed levels around the intake point of the side channel and the effect of the bed levels
in the navigation channel. The model has a mobile bed composed of light weighted
polystyrene to simulated the bed load transport in the channel. The relative density of the
material in water is 1.055. In polystyrene dunes are developing in equal proportions to dunes
in the prototype river. The applied flow velocity in the model is based on a scaling analysis of
the dimensionless bed shear stress.
Laser scan results of the bed level shows that during low discharge the training dam has a
positive effect on the bed levels in the navigation channel. The interpretation of the model
results and the translation to the prototype is mainly focussing on the spatial pattern of
erosion and sedimentation and the relative bed levels.
16
Figure 1 Location of training dam (yellow) and intake weir (orange) at the inner bend of the
river.
Figure 2 Overview of flume with groynes, training dam and intake weir.
17
Experimental rivers: from braided towards meandering by the addition
of cohesive floodplain material
W.M. van Dijk, W.I. van de Lageweg and M.G. Kleinhans
Faculty of Geosciences, Department of Physical Geography, Utrecht University, PObox 80115,
3508 TC Utrecht, The Netherlands ([email protected]) Braided rivers are relatively easily formed in the laboratory, whereas self-formed
meandering rivers have proven very difficult to form. Our objective is to create self-formed
dynamic braided and meandering rivers in a laboratory, and to quantitatively compare the
resulting morphology and deposits. We applied a transverse moving inlet funnel for flow and
sediment at the upstream boundary, mimicking meanders migrating into the control section.
Conditions in the meandering and braided experiment were exactly equal except that slightly
cohesive silt-sized silica flour was added to the feed sediment of the meandering channel.
This was to test the hypotheses that 1) meandering rivers have relatively narrower and
deeper channels due to bank cohesion, and 2) that floodplain-filling sediment fills potential
chute channels that would otherwise lead to braiding.
Our experiments were conducted in a flume of 10x6 meter, which was split up into two
separate fluvial plains (each 10x3 m). The parallel setups have identical cycled discharge
regimes with a longer duration low flow and a shorter duration high flow simulating floods.
The bed sediment consisted of a poorly sorted sediment mixture ranging from fine sand to
fine gravel. The evolution was recorded by high-resolution line-laser scanning and digital
Single Lens Reflex (SLR) camera used for channel-floodplain segmentation and particle size
estimation.
In agreement with earlier work, the experimental river without silica flour evolves from
alternate bars to a fully braided river. With silica flour added to the feed, a meandering
system evolved with frequent chute cut-offs that nevertheless remained mostly single-thread.
The silica flour introduces cohesive self-formed floodplains, causes narrower channels and
fills potential chutes. Large bends developed with scroll bar complexes and sinuosity reached
maxima of 1.4. In contrast, the non-cohesive experiment is dominated by much more rapid
channel shifting and displacement, so that much more sediment was reworked. Apparently,
the lack of bank cohesion allowed more sediment to be available within the channels, which
in turn enhanced the braiding tendency. We conclude that the increase of fine cohesive
material leads to a decrease in chute cutoffs and the tendency to braid. The upstream moving
inflow boundary was a necessary condition for dynamic meandering and braiding.
18
Do invasive benthic mollucs impact river morphology?
Felipe A. Elizondo García, Denie C.M. Augustijn, Bas W. Borsje, University of Twente, Water
Engineering and Management
Rob S.E.W. Leuven, Radboud University Nijmegen, Institute for Water and Wetland Research The invasion of exotic benthic mollusc species in aquatic systems has increased in the last
couple of decades due to the construction of a European network of waterways and an
increase in shipping activities (Leuven et al., 2009). Many studies have been done on the
interaction between benthic organisms, sediment dynamics and thus morphology of aquatic
systems. However, most of these studies have been conducted in marine and estuarine
systems, involving different types of sediment and hydrodynamic conditions. Until now no
studies are known on the impact of benthic species on river morphology.
The main objective of this study was to investigate the influence of benthic species on
sediment dynamics and river bed morphology. The study considers three exotic bivalve
species in the River Waal: the Asian clam (Corbicula fluminea), Zebra mussel (Dreissena
polymorpha) and Quagga mussel (Dreissena rostriformis bugensis). The Zebra and Quagga
mussels prefer hard substrate. In the Dutch rivers they are mainly attached with byssus
threats to groyne stones, rip rap and other benthic molluscs. Asian clams live on sand and
muddy substrates. Because of the high flow velocities in the main channel they are mainly
found in the groyne fields.
Benthic species can affect sediment dynamics in several ways: filter feeders can increase the
sedimentation rate by filtration of the water column and deposition of stable faecal pellets or
loose pseudofeces; pedal feeders can loosen the sediment by burrowing for food
(bioturbation) and hence decrease the erosion threshold. In addition, bivalves can physically
cover the sediment which increases erosion at low densities due to increased turbulence and
decrease erosion at high densities when most of the sediment is covered. The filtration rates
of the considered species can be neglected compared to estimated settling velocities. This
leaves the Asian clam as the only species exerting a direct impact on sediment. They can
stabilize the sediment at high physical coverage and by excretion of faecal pellets and the
stimulus of biofilm formation or destabilize the sediment at low physical coverage. The effect
of bioturbation was assumed to be irrelevant in non-cohesive sediment.
In order to evaluate the possible benthic effects, three scenarios were implemented in a
calibrated Delft3D model for a part of the River Waal obtained from Deltares: a scenario with
biostabilization (increased erosion threshold), a scenario with biodestabilization (decreased
erosion threshold) and an extreme scenario that accounts for the anticipated maximum
possible biostabilization in rivers. When using the transport formulation developed by Van
Rijn (1984), the erosion threshold is proportional to the median grain size D50, and therefore,
in this study this value was locally increased/decreased inside the groyne fields in order to
introduce the benthic effects into the Delft3D model. The results show that under steady
hydrodynamic conditions the benthic organisms are not expected to have significant impact
on morphology. Variable flow regimes and navigation are expected to alter the sediment
processes within the groyne fields and therefore the benthic impact. These conditions were
not considered in this study and are recommended for future research.
References:
Leuven, R.S.E.W., G. van der Velde, I. Baijens, J. Snijders, C. van der Zwart, H.J.R. Lenders, A. bij
de Vaate, 2009. The river Rhine: a global highway for dispersal of aquatic invasive species.
Biological Invasions 11(9): 1989-2008.
19
Van Rijn, L. C., 1984. Sediment transport, Part I: bed load transport. Journal of Hydraulic
Engineering 110 (10): 1431-1456.
20
Quantifying vegetation succession in floodplains using map series
Giel Ermers, Department of Environmental Science, Radboud University Nijmegen1
Gertjan Geerling, Deltares, Utrecht2
Emiel Kater, Alterra institute, Wageningen University
Rob Lenders, Department of Environmental Science, Radboud University Nijmegen
Rob Leuven, Department of Environmental Science, Radboud University Nijmegen
Control of hydraulic roughness by maintenance of floodplains is an important and urgent
measure of sustainable river management. Control and clearance of floodplain vegetation,
particularly softwood forests, is currently performed within the ‘stroomlijn’ program and
will be executed on a regular basis. Accurate planning and modelling of vegetation
development can help to reduce management costs: on the one hand by designing a more
robust or self-sustaining system and on the other hand by improved predictions of future
vegetation development. The use of remotely sensed maps for monitoring and hydraulic
modelling of floodplains is common practise. However, modelling of vegetation succession
along rivers based on analysis of time series of maps has not been applied extensively. The
key question is, what insight on vegetation succession rate and transitions can be gained
using change matrices derived from these time series.
Time series of vegetation maps of various locations were used to create sequences of change
matrices. Succession is interpreted as a linear process, with gain of biomass as the main
character of succession. The vegetation classes used in the maps were standardised to a fixed
vegetation structure class set. This resulted in a set of time series of vegetation development
covering 20 to 40 years. With these maps succession trajectories and change dynamics of
floodplain vegetation were quantified in GIS. As a result, the development of the different
vegetation classes is visualised for various floodplains, showing succession rates, succession
trajectories and landscape configuration. Finally, the uncertainties concerning data scale and
quality, quantification of succession and vegetation classification are discussed.
The results made clear that the Ewijkse Plaat and the Allier section show a dynamic
behaviour, in which also rejuvenation takes place. On the other hand, the Blauwe Kamer
shows a much more stable system with few transitions and hardly rejuvenation. Moreover,
the scarcity of bare soil and pioneer vegetation in the Blauwe Kamer displays the absence of
rejuvenation, contrary to the other floodplains. All three floodplains show a net gain of total
biomass, which means they are in succession. The speed of this succession is expressed in a
graph presenting the extent of the transitions (area times step size), according to our linear
succession model. The slope of the trend line is a possible quantitative indicator for the speed
of succession. Succession is also expressed for the different categories, showing relations
between the classes and showing differences between the areas. The results are a basis for
incorporating succession into a more extended model (hydraulic or ecological). For this, more
field data from different floodplains should be acquired, in order to calibrate the model.
Furthermore a algorithm should be applied, that calculates the effects of a specific transition.
1 Giel Ermers (corresponding address): [email protected]
2 Gertjan Geerling (supervision): [email protected]
21
Morphological aspects of cyclic rejuvenation of the section scale
(Ewijkse Plaat) and reach scale of the Waal River, the Netherlands
E. Facchini 1, 2, V. R. S. Putra*1, A. Crosato**1, P. Paron***1
1UNESCO-IHE, Dep. of Water Engineering, Delft, the Netherlands 2Universita degli Studi di Firenze, Facolta di Ingegneria, Italy
Correspondence to:
*Email: [email protected], ** Email: [email protected], ***Email: p.paron@unesco-
ihe.org
PO Box 3015, UNESCO-IHE, Dep. of Water Engineering, 2601 DA Delft, the Netherland
Rhine River floodplains are becoming
narrower, disconnected from channel and
losing their ecological function as an effect of
being regulated during the past centuries.
The rehabilitation of this regulated river
should consider natural process such as
sedimentation and growth of vegetation
without ignoring safety against floods. Cyclic
Floodplain Rejuvenation (CFR) is a strategy
that was conceived to rehabilitate and
minimize negative effects of River Rhine
dynamics by cutting vegetation and lowering
of floodplain.
The section scale study was carried out to
answer the challenges of joining (1) river
restoration aiming to give more room to
vegetation and geomorphologic processes
and (2) river safety by improving the
discharge capacity at the Ewijkse Plaat (a
floodplain on the Waal River - part of River Rhine). This study will be continued with an
analysis at the reach scale, which is here anticipated.
The previous section scale study was aiming at understanding the vegetation-sedimentation-
flow dynamics and at formulating general hypothesis about the optimization of rejuvenation
strategies. These goals were achieved by building numerical model with Delft3D software,
developed by WL/Delft Hydraulic (now Deltares). A previous model of the Waal River, built
by Deltares, was cut on the study area, modified to reproduce hydrodynamic and
morphological processes, then calibrated and validated with field data. After model validation,
4 scenarios were simulated: (a) periodic vegetation cut strategy applied every 5 years for 20
years; (b) free vegetation growth for 20 years; (c) an alternative excavation of the Ewijke
plaat (d) re-opening of a former side channel near Ewijkse Plaat.
The numerical reproduction of the Ewijkse Plaat evolution proved to be reliable, as far as
sedimentation rates and patterns are concerned. The main findings were that two alternative
solutions (excavation of drainage channel and side channel opening) lead to hydrodynamic
benefits which do not decrease in the short term. It was also demonstrated that periodical
vegetation cut (every 10 years) helps in decreasing the sedimentation also at a cross sectional
scale, but to decrease water levels it needs to be applied on a reach scale.
Figure 1 Floodplains along dutch rivers. Ewjikse
Plaat is in the rectangle (modified from
Middelkoop [1997])
22
The importance of Waal River for navigation triggers the next study to focus on the effect of a
more refined spatial and temporal vegetation succession that will be applied to floodplain at
reach scale of Waal River. The Ewijkse plaat is a part of this reach scale study. In this new
study vegetation growth patterns will be modelled at seasonal temporal scale instead of
annually, and different vegetation cover types will be considered instead of homogeneous
ones.
23
Self Supporting River System to reduce maintenance
Havinga, H.
Dutch Ministry of Infrastructure and Environment, Rijkswaterstaat, Dienst Oost-Nederland
Delft University of Technology, Faculty of Civil Engineering
By 2015 a vast number of flood protection measures (Room for the River, RVR) and river
restoration plans (European Water Directive Framework, WFD) will be completed. Within
the scope of these programs measures are prepared that will increase the dynamics in the
floodplains and at the river banks. The creation of numerous side channels, free banks and
the growth of natural vegetation will complicate daily river management, as it may be
expected that navigation will be hampered by shoals in the low water bed and flood
protection will be reduced by unregulated vegetation succession. In fact, river administration
will evolve from an administrative type of management with license and permits into a form
of Dynamic River Management, that also includes a system of frequent monitoring,
forecasting of flood and bed levels and pro-active, c.q. corrective maintenance measures. Such
a system of Dynamic River Management demands more personnel and budget, besides
specific know-how of morphology and ecology, in order to take appropriate measures.
Regarding global and national developments in economy and governmental organisations, it
may be expected that these demands cannot be met. As a consequence the functions inland
navigation and flood protection may be in jeapordy. With this in mind other ways of river
management are explored to cope with the enormous amounts of dredged spoil and
vegetation waste that can be expected after implementation of the RVR and WFD
programmes.
The tradional way to cope with the demands of different river functions is to alter the lay-out
of the river system in order to satisfy these demands. The impact of varying discharges in the
form of sedimentation and erosion of the low water bed is counteracted by dredging. Today
systematic dredging instead of structural measures like groyne adaptations or longitudinal
dams is often seen as a measure to fight decreasing sailing depth’s caused by shoals. E.g. the
navigation channel of the Waal River is kept continuously larger than the equilibrium channel
by dredging of around 400.000 m3/yr, that has to be dumped in the low water bed to prevent
bed erosion. It is expected that the RVR and WFD measures will give rise to extra dredging
activities costing € 3 million/yr for the Waal River and IJssel River. Nevertheless, the author
expects that even with this budget available, navigation and flood protection demands
eventually cannot be met, so in his view (also) structural measures are demanded.
Capitalisation of the yearly maintenance is way too less to justify structural measures along
the lines of Life Cycle Cost (LCC). However, if use is made of the dredged spoil and vegetation
waste (trees, branches) to build temporary structures (e.g. longitudinal dams) money can be
saved. From the vegetation waste provisional gabions can be built, that can serve as
containers for the dredged spoil. Using 2D morphological predictions these temporary
structures can be erected at appropriate sites at or near known sites with shoals. This
process saves money to transport the dredged spoil and vegetation waste and at the same
time sedimentation is temporarily (e.g. 2-4 years) reduced by the structure.
The program Self Supporting River System reasearches possibilities to set this process in
motion, using interested third parties. As a start a project is prepared to tender a contract of 5
or 10 years with the obligation to reduce the amount of dredging from 100% in the first year
to 10 % in the last year.
24
Discharge estimation in a backwater affected meandering river
H. Hidayat1,2, B. Vermeulen1, M. G. Sassi1, P. J. J. F. Torfs1, and A. J. F. Hoitink1,3
1Hydrology and Quantitative Water Management Group, Wageningen University, Wageningen,
The Netherlands
2Research Centre for Limnology, Indonesian Institute of Sciences, Cibinong, Indonesia
3Institute for Marine and Atmospheric Research Utrecht, Department of Physical Geography,
Utrecht University,
Utrecht, The Netherlands
Contact detail: H. Hidayat ([email protected])
Hydrology and Quantitative Water Management Atlasgebouw (104),
Droevendaalsesteeg 4, P.O. Box 47, 6700 AA, Wageningen
Tel: +31-317-482765 Variable effects of backwaters complicate the development of rating curves at hydrometric
measurement stations. In areas influenced by backwater, single-parameter rating curve
techniques are often inapplicable. To overcome this, several authors have advocated the use
of an additional downstream level gauge to estimate the longitudinal surface level gradient,
but this is cumbersome in a lowland meandering river with considerable transverse surface
level gradients. Recent developments allow river flow to be continuously monitored through
velocity measurements with an acoustic Doppler current profiler (H-ADCP), deployed
horizontally at a river bank. This approach was adopted to obtain continuous discharge
estimates at a cross-section in the River Mahakam at a station located about 300 km
upstream of the river mouth in the Mahakam delta. The discharge station represents an area
influenced by variable backwater effects from lakes, tributaries and floodplain ponds, and by
tides. We applied both the standard index velocity method and a recently developed
methodology to obtain a continuous time-series of discharge from the H-ADCP data.
Measurements with a boat-mounted ADCP were used for calibration and validation of the
model to translate H-ADCP velocity to discharge. As a comparison with conventional
discharge estimation techniques, a stage-discharge relation using Jones formula was
developed. The discharge rate at the station exceeded 3250 m3s−1. Discharge series from a
traditional stage-discharge relation did not capture the overall discharge dynamics, as
inferred from H-ADCP data. For a specific river stage, the discharge range could be as high as
2000 m3s−1, which is far beyond what could be explained from kinematic wave dynamics.
Backwater effects from lakes were shown to be significant, whereas interaction of the river
flow with tides may impact discharge variation in the fortnightly frequency band. Fortnightly
tides cannot easily be isolated from river discharge variation, which features similar
periodicities.
25
Exploring the ecological benefits of water level management in
impounded rivers: case study River Meuse (the Netherlands)
Leon van Kouwen1*, Gertjan Geerling1, Tom Buijse1, Frans Kerkum2, Kees Sloff1, Johan van
Zetten1 & Gerben van Geest1
1 Deltares, Princetonlaan 6, 3584 CB Utrecht, the Netherlands 2 Ministry of Infrastructure and Environment, RWS Centre for Water Management,
Zuiderwagenplein 2, 8224 AD, Lelystad, the Netherlands
* phone: +31653798668; e-mail: [email protected]
Introduction
The Meuse has a length of 925 km and a catchment area of 36,000 km2. It is a rain-fed river
with unpredictable discharges averaging 230 m3s-1, but ranging from 20 to 3,100 m3s-1. It has
undergone many modifications. Dykes have been built, banks have been fixed and weirs have
been installed for water level stabilization.
Alteration of weir management is a potential measure to improve the ecological status of the
Meuse, which is currently poor to moderate. We assessed options for altered management of
three of its seven weirs, focusing on ecological benefits.
Methodology and results
We modeled the water level using a 1-D hydrodynamic model for the prediction of water
levels within the impoundments. Water levels appear to vary at high discharges (>200 m3s-1)
in upstream parts. Here, water level variation is 0.8 to 1.4 m for discharges occurring seven
days in the growing season and 0.2 to 0.4 m for discharges occurring 30 days in the growing
season. In total, water level variation is less than 0.2 m for about half of the shorelines.
The morphological classification distinguished between natural and protected shorelines.
The latter is of little ecological value. We then applied the typology to the main channel of the
Meuse, taking all planned measures for removal of shoreline protection by 2015 into account.
A literature review on the ecological response to water level variations yielded conceptual
frameworks, stating that many aspects of water level variation are important. However, no
thresholds were offered to support decision making. We decided to follow natural water level
variation by lowering the water level 30 cm at low discharge (see Figure 1). With this
scenario, water level variation increases upstream as well as downstream in the
impoundments.
26
2
3
4
5
6
7
8
0 200 400 600 800 1000 1200 1400
Waterpeil(m NAP)
Discharge (m3s-1)
Grave (upstream)
Lith (upstream)
Lith (downstream)
Wa
ter
lev
el
(m+
NA
P)
B
A
Figure 1 Scenario which follows discharges at Borgharen. The dark-gray dotted line shows
the water level upstream in the impoundment at Lith. The light-gray dotted line shows the
water level variation downstream in the impoundment. At discharges higher than 600 m3s-1,
the water level follows the current regime.
We then combined the modeled current water level variation and the scenario with our
typology of the main channel using GIS analysis. We quantified the change in water level
variation for natural and protected shorelines in the main channel (Figure 2). Most shorelines
move up a few classes. The length of protected shorelines now experiencing little water level
variation is high compared to the length of natural shorelines.
27
The influence of floodplain vegetation succession on hydraulic
roughness: is nature restoration in Dutch embanked floodplains
compatible with flooding safety standards?
Bart Makaske1,*, Gilbert J. Maas1, Claus van den Brink2 and Henk P. Wolfert1
1 Alterra, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The
Netherlands; 2 Duurzame Rivierkunde, Hoenloseweg 3, 8121 DS Olst, The Netherlands
* Corresponding author; E-mail: [email protected] We present a recently published study (Makaske et al., 2011) in which we show for one of the
Dutch Rhine River branches that large-scale riverine nature restoration and related
vegetation succession may lead to up to 0.6 m higher river flood levels, because of increased
hydraulic roughness. We hydraulically modeled future succession stages of embanked
floodplain vegetation, following from present nature restoration plans for the 124-km-long
river IJssel, and found flood levels exceeding the safety levels (related to dike heights). We
used a 2DH hydraulic model that meets all requirements of the Dutch Directorate-General for
Public Works and Water Management (Rijkswaterstaat). Our models took into account the
river engineering measures presently carried out in the context of the ‘Room for the River’
project, which aims at enhancing the river discharge capacity in order to meet required safety
standards. Our study shows that there is a pressing need for integrated hydraulic-ecological
evaluation of river engineering measures and nature restoration plans in the Rhine
embanked floodplains. An important conclusion also is that hydraulic evaluation of planned
vegetation goals only is inadequate, because flow resistance of preceding succession stages
may be higher.
Reference:
Makaske, B., Maas, G.J., Van den Brink, C. & H.P. Wolfert (2011) The influence of floodplain
vegetation succession on hydraulic roughness: Is ecosystem rehabilitation in Dutch
embanked floodplains compatible with flood safety standards? AMBIO 40 (4), pp. 370-376.
28
Hydropolitics of Hirmand river, water dispute between Iran and
Afghanistan
Mianabadi, Hojjat1; Mostert, Erik 1 1Delft University of Technology, Netherlands.
Iran has at least fifteen neighbours, one of the largest number of neighbours in the word.
Since it neighbours Afghanistan and Iraq, who live in the worst insecurity conditions and war
situation, the Iranian border circumstances have been critical. In addition to this, Iran has an
extremely significant geopolitical and geo-strategic position between the Persian Gulf and
Caspian Sea energy depots. Given this situation, it can be concluded easily that Iran has one of
the largest cross-border tensions in the world.
Worsening the situation is the fact that the water scarcity crisis is particularly severe in this
region and water has the potential to threaten regional peace. It has been suggested that the
scarcity of water will be a key factor in any future conflict in this region. Under these
circumstances, the equitable and reasonable use of the transboundary rivers, such as the
Euphrates-Tigris, Hirmand and Amudarya rivers, stands at the heart of political conflict
among riparian states and deeply impacts their present and future relations. In other words,
Iran not only suffers from water scarcity and insecurity in her neighbouring countries, but is
also significantly involved in political disputes resulting from myriad and inequitable use of
shared transboundary rivers by riparian states.
Iran has transboundary rivers with seven neighbours, and around 22 per cent of its land
border consists of boundary rivers. Against this background, it is necessary to examine and
study Iran’s transboundary rivers comprehensively in order to reduce the causes of friction
with the other riparian states. Among Iran’s transboundary rivers, the Hirmand river, which
forms the common border between Iran and Afghanistan, is of particular importance for both
countries. Hence, on this poster we present the water dispute between Iran and Afghanistan
on the Hirmand river. Furthermore, the treaties between these countries are briefly reviewed.
The results of this study show that in spite of several treaties and agreements, this conflict is
rooted more than one hundred years and both riparian countries should be committed to
their treaties and consider this river as a transboundary and international river.
29
Reconstructing palaeo peak flow regimes for the river Rhine
Michiel M. de Molenaar(1,2), A.H. te Linde(1), H. Middelkoop(2)
(1) Deltares
(2) Department Physical Geography, Utrecht University Introduction
To determine magnitude and recurrence times of extreme discharges (recurrence time in the
order of 1000 yr) of the lower Rhine River, the observation record of Rhine discharge is too
short (100 – 150 yr). Therefore, to obtain more reliable estimates of extreme peak flows, we
need information from historic sources and from sedimentary data from the Rhine floodplain
that have documented extreme flows over the past centuries to millennia. In a joint project of
the Department Physical Geography (UU) and Deltares carried out by Toonen, flood layers
from sediment records in the Rhine delta are presently investigated for this purpose.
However, to convert the flood layers in these records to flood magnitude, we must account
for the large changes in the Rhine basin and along the Rhine river that have occurred due to
human interference. These include land use changes in the Rhine basin, as well as settlement
along the river, embankment, and numerous engineering projects along the main river.
Consequently, precipitation events that lead to a certain magnitude flood under present day
conditions, might have resulted in considerably different peak flows under pre-human
conditions. Thus, we need to know to what extent these human influences have affected the
peak flows in the Rhine.
Objective
The general objective of this project is to determine the peak flow regime and associated
flowrecurrence times of the lower Rhine River that would result from present-day
precipitation in a Rhine basin not influenced by man. The results should allow to determine
to what extent land use changes and engineering works along the main river have affected
peak flows. Furthermore, the results should provide more reliable estimates of historic and
palaeo-peak flows that are reconstructed from historic and sedimentological data.
Approach
In this project the hydrological and hydraulic simulation models available at Deltares (Sobek)
are used for building a new model of the River Rhine for pre-human conditions. Using this
model, peak flows are simulated using time series of historic floods for the pre-human Rhine.
The results are compared to present-day conditions.
Building the models comprises:
1 –Reconstruction of the pre-human landscape in the form of a Digital Elevation Map (DEM).
This is done using various palaeo geographic reconstructions from other researches. The
vegetation roughness is derived from a previous study into maximum palaeo discharges of
the River Rhine.
2 – The building of a SOBEK 1D hydraulic model of the main river for the pre-human situation.
Cross sections for the main river were derived from borings in residual channels and
transects in previous studies. The course of the main channel is derived using the same
studies in combination with interpretations of the DEM.
Using the newly constructed models, synthetic simple flood peaks were simulated as well as
historic discharges of, for instance, the 1993 and 1995 floods. The resulting discharge series
at the downstream point (Rees, Germany) was converted to stage-discharge curves, and using
the prehuman discharges, a new discharge-recurrence times relationship was established. By
30
comparing the different model outcomes to the present day stage-discharge curves the
influence of human activities on the peak flow regime of the River Rhine was determined.
Results and interpretation
The result of this study is a combined 1D2D model of the River Rhine in pre-human times.
The outcome of the simulation runs using this model shows a dampening of flood peaks,
decreased water levels and a lower celerity of the peaks compared to the present day
situation. The simulations also show that the degree of dampening is highly depending on the
morphology, the total volume and the number of consecutive discharge peaks. They show
that for smaller, single flood peaks (up to roughly 10,000 m3/s), dampening is considerable
(up to 30% of the peak discharge), while for more extreme peaks (10,000 m3/s and higher)
dampening is marginal (around 5%). When multiple flood peaks over a short time period are
simulated, the dampening decreases with each consecutive flood peak. This is attributed to
the lateral discharge of water onto the floodplains when the water carrying capacity of the
main channel is exceeded. During smaller, single flood peaks, the volume of water that is
laterally discharged to fill the accommodation space of the floodplains will dampen the flood
peaks. For larger flood peaks, this accommodation space is already filled before the actual
flood peak passes, causing only very limited dampening of the flood peak. The same holds for
flood conditions with multiple flood peaks. Both in the present-day and historic situation this
floodplain storage of water will occur during such extreme floods. Generally, after the first
flood peak the accommodation space on the floodplains will be filled, after which the
following flood peaks will see only marginal dampening. Still, for all flood peaks, the decrease
in celerity compared to the present day situation remains fairly stable.
Conclusions
When the simulation outcomes are compared to the current day recurrence times graph, only
the recurrence times of smaller (single peaked) floods increase considerably, while the
recurrence times of more extreme floods are roughly the same as under present-day
conditions. This implies that for reconstructed extreme historic and palaeo flood discharges
only minor corrections are required to convert these to present-day discharges.
31
Reconstruction of the early 19th century Waal River
Alejandro Montes Arboleda1, Alessandra Crosato1, 2,* and Hans Middelkoop3 1 UNESCO-IHE, Department of Water Engineering, PO Box 3015, 2601 DA Delft, The Netherlands
2 Delft University of Technology, Section of Hydraulic Engineering, PO Box 5048, 2600 GA Delft,
The Netherlands 3 Utrecht University, Faculty of Geosciences, PO Box 80.115, 3508 TC Utrecht, The Netherlands
We reconstructed the River Waal situation in the early 1800s, providing a basis for
establishing the long-term effects of the “normalisation” works, which were carried out
between 1850 AD and the early 20th century. Historical discharge hydrographs were derived
from a correlation between flow discharge records at Cologne, Germany, and water level
measurements of the Rhine branches in the Netherlands, taking into account the discharge
distribution between the branches. The bed topography was derived from reconstructed
cross-sectional profiles (Maas et al., 1997). Historical maps of vegetation cover were derived
from reconstructed ecotope maps (Maas et al., 1997).
Available historical data do not include suspended sediment concentrations before the 20th
century (Asselman, 1997). We used a 2D physics-based morphodynamic model based on the
Delft3D code, together with independent estimates of historical floodplain sedimentation
rates by means of geomorphologic field work (Middelkoop, 2002), to fill in this gap. The
model accounts for the influence of floodplain vegetation on river moprphodynamics,
following the method by Baptist (2005) and simulates sedimentation on vegetated
floodplains, since it can treat the processes of fine sediment.
The computed historical sedimentation rates are found to be within the range of measured
data, which suggests that fine suspended sediment concentrations in the early 1800s were
comparable to contemporary ones.
References
Asselman, N.E.M. 1997. Suspended sediment in the river Rhine. Netherlands Geographical
Studies. PhD thesis, University of Utrecht, Utrecht, the Netherlands, ISBN 90-6266-150-5.
Baptist, M. J. 2005. Modelling Floodplain Biogeomorphology. PhD thesis, Delft University of
Technology, Delft, the Netherlands, ISBN 90-407-2582-9.
Maas, G. J., Wolfert, H. P., Schoor, M. M. & H. Middelkoop 1997. Classificatie van riviertrajecten
en kansrijkdom voor ecotopen, Report 552, DLO-Staring Centrum, Wageningen, the
Netherlands (in Dutch).
Middelkoop, H. 2002. Reconstructing floodplain sedimentation rates from heavy metal
profiles by inverse modelling. Hydrological Processes, 16(1), 47-64. DOI: 10.1002/hyp.283.
32
Parameterization of bank shear stresses in curved open channel flow
based on large-eddy simulations.
Willem Ottevanger
Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands
Koen Blanckaert
State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental
Sciences, Chinese Academy of Sciences, Beijing, China
Laboratory of Hydraulic Constructions (LCH). Ecole Polytechnique Fédérale de Lausanne (EPFL),
Station 18, Lausanne, Switzerland
Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands
Wim S.J. Uijttewaal
Faculty of Civil Engineering and Geosciences, Delft University of Technology, The Netherlands Meandering rivers and streams are a common planform in the world’s populated areas.
Furthermore the recent increased focus on renaturalization projects has lead policy makers
to also consider the partial remeandering of previously trained rivers. Economic factors such
as navigation, man-made infrastructure and valuable farm land set the boundary conditions
for such rivers. Understanding the behavior of the near bank flow in schematized open
channel bends could help in understanding the behavior of meandering rivers and predict
locations of potential damage, as well as aid in the development of design criteria of stable
river banks.
The flow in curved open channels exhibits complex flow structures (such as the outer bank
cell) near the outer bank which may play an important role for the magnitude and
distribution of the bank shear stress. To accurately model these flow features a flow solver
with an advanced turbulence closure is necessary.
A large set of axi-symmetric simulations (infinite length bend) were performed
using a well-validated large-eddy simulation code. A wide range of mildy and sharply curved
bends represented by the parameter space B/R (width to radius of curvature ratio) and Cf-
1H/B (width to depth ratio normalized by the friction factor) were considered.
Considering the bank shear stress to depend quadratically on the sum of the velocity excess
and the bulk velocity multiplied by a bank friction factor Cf,bank, a correction factor ψouter bank is
derived. The correction factor ψouter bank, which depends on B/R and H/B, represents the
increase of bank friction factor compared to a straight channel flow due to the complex
curved outer bank hydrodynamics.
33
2D-morphological modelling of side channels
D.R. Van Putten1, F. Hoefsloot1, R. van der Mark2, R.M.J. Schielen3, J.S. Ribberink4 1CSO, 2Deltares, 3Ministry of Infrastructure and Environment/Twente University, 4Twente
University
Several side channels are planned in the Netherlands currently, for increasing the safety
against floods. However, the morphological consequences of this measure in the long term
are still uncertain. From a previous 1D-studie with SOBEK it is known that a side channel
could silt up within 10 years, which is undesirable for maintenance costs.
The main trigger behind morphological behaviour is the distribution of sediment into the
main and side channel. In 1D this division is calculated in a nodal-point-relation (from Wang
et al. 1995), which does not allow to incorporate geometric and physical characteristics
directly. Therefore 2D-modelling (depth-averaged) in Delft3D is applied within this research,
which allows to research the sensitivity of geometric and physical characteristics. In order to
do so, an idealised system of a straight main channel with a side channel of 1,5km long was
created. The input (discharge, gradient, width, etc.) were based upon the Waal river. Initially
the side channel discharged 3% of the main channel, and the bed level was 3,5m higher than
the main channel.
The 2D morphological reaction of the main channel is the formation of alternating bars in the
first years after construction of the side channel. These bars developed downstream of the
side channel, migrated further downstream and were replaced by fixed bars. Directly after
construction of the side channel an erosion pit of 18cm developed downstream the side
channel. Within four years it migrated 4km downstream outside the domain.
The width-averaged results show that an morphological equilibrium is reached after 15 years.
By then, the side channel was heavily eroded (2,6m) and discharging about 9,5% of the
discharge in the main channel. The severe erosion was probably due to the design of the
bifurcation, directing much discharge to the side channel.
The description of the equilibrium bed level in the main channel is divided in three sections.
Downstream the bed level is equal to the initial bed level. At the location of the side channel
large sedimentation (45cm) occurs. Upstream of the side channel very small sedimentation
(9mm) takes place. Though this seems a small amount, it is exactly the water level reduction
initially created by the construction of the side channel. A closer look at the water level shows
that the initial reduction in water level changed in an increase of water level of 9mm at the
equilibrium situation.
The influence of several parameters was also tested within this research. The parameters
tested are bifurcation angle, sedimentsize, a calibration factor for spiral flow, a calibration
factor for sediment-transport and an upstream bend. From these parameters only the
upstream bend was really influencing the morphological response in the side channel. The
main cause for the sensitivity of the bed level of the side channel is the presence of a point bar
or a pit at the entrance of the side channel. With a point bar the equilibrium bed level of the
side channel was substantially higher than with a pit, with a maximum difference of 3,5m.
The width-averaged results for the main channel corresponded reasonably well with
analytical studies. 1D-results however, disagreed with the 2D- and analytical results. This is
mainly because the effects of the nodal-point-relation of Wang et al. (1995) were not seen in
2D or analytical studies. According to 1D-results, instability could occur and lead to siltation
34
of the side channel. However, siltation of the side channel could not be reproduced within 2D,
despite the fact that the conditions for instability were met. Therefore it is concluded that the
nodal-point-relation of Wang et al. (1995) is not applicable to predict the morphological
behaviour of a side channel.
35
Dynamic stage-discharge relations of the Dutch Rhine branches
S. Quartel1, R. van der Veen2, A. Wijbenga3, F. Berben1, F. Kok1 & P. Heinen4
1 RWS Dienst Oost-Nederland, 2 Rura-Arnhem, 3 HKV, 4 RWS Waterdienst Reliable discharge time series for rivers are fundamental components within effective river
management: e.g. flood (risks) management, navigation, environmental redevelopment.
Although the measuring techniques for continuous discharge time series are constantly
evolving, the technique for continuous water level measurements is more frequently applied
and more straight forward. Dutch discharge time series were therefore mainly derived from
water level time series by use of a static rating curve, which presents a direct relationship
between the discharge and water level stage.
The development of a rating curve does require discharge data. Discharge measurements are
executed during various water level stages, but collected with irregular time intervals. The
stage-discharge relation needs to be checked frequently against these discharge
measurements due to constant changes in the river system. Analysis of the historical static
rating curves (1901-2001) of Lobith showed the temporal variation of the stage-discharge
relation and its liaison with autonomous subsidence of the river bed (Van Vuuren, 2004;
Figure 1). On a shorter timescale, hysteresis causes temporal variation in the stage-discharge
relation. Whereas rating curves reflect steady-state conditions, unsteady flow conditions as
hysteresis lead to a looped rating curve.
Figure 1 Different rating curves (Qh 1986, 1990, 1996 and 2000.1) together with the
discharge measurements from 1956 - 2008 show the temporal change of the stage-discharge
relation of Lobith
In need to incorporate temporal variations, dynamic stage-discharge relations were
developed for several locations along the Dutch Rhine (Ogink & Stolker, 2004; HKV, 2010).
The relation also takes into account the effect of weirs and changes made to the river system
due to large projects as Room for the River. The methodology comprises physical
backgrounds (e.g. Jones correction) and statistical techniques to optimise the result.
36
This presentation will clarify the methodology of this dynamic stage-discharge relation and
the improvement of the derived discharge time series. Additionally, it will discuss the impact
of this relation for Dutch river management.
References
HKV (2009). Beheer en onderhoud afvoerreeksen Rijntakken, deelonderzoek A:
Operationaliseren Qf-relatie Bovenrijn, Waal, Pannerdensch Kanaal, Nederrijn en IJssel,
rapport PR1444.20.
Ogink, H.J.M. & Stolker, C. (2004). Verbetering Qf-relaties, WL|Delft Hydraulics, rapport
Q3847.00.
Van Vuuren, W.E. (2004). Een analyse van de temporele ontwikkeling in de historische Qh-
relaties van de Bovenrijn bij Lobith in de periode 1901-2000, memo WSR 2004-019.
37
Optimal anticipatory control of river structures using Ensemble
Forecasting System
L. Raso1 – D. Schwanenberg2 – P.J. van Overloop1 – N. van de Giesen1
! Delft university of Technology. 2 Deltares Presently, the most common technique for supervisory management of hydraulic structures
is the definition of explicit operating rules. For example: minimum releases for reservoirs due
to the reservoir level and environmental objectives, the operation of flood detention basins
based on water level at reference locations, or the definition of set points for upstream water
levels of river weirs. This control method is straightforward to apply, although local and non-
anticipatory.
Model Predictive Control (MPC) is a concept which has been widely applied in control of
industrial process over the last two or three decades and has showed promising results for
water systems as well. Its key elements are: (1) a model of the physical process for predicting
future trajectories of the controlled variables over a finite horizon. (2) the calculation of a
control sequence that optimize an objective function. (3) a receding strategy: at each instant
the first signal of the control sequence is applied and the horizon is displaced towards the
future.
The control obtained using MPC is a global optimum: this allows a centralized management
and guarantees a harmonic control of complex and strongly interconnected systems, as the
Dutch river delta is. MPC exploits the information contained in the forecast: before the
realization of the disturbance, the control sequences set the system to a state which is
optimal to accommodate the disturbance. This capacity of anticipation is a clear improvement
on reactive operating rules presently used.
An ensemble is a set of possible future trajectories of a meteorological system, where the
main sources of uncertainty are addressed by running a numerical weather prediction model
altering the initial conditions or using diverse numerical representations of the atmosphere.
Tree-based MPC uses the ensemble as an input for setting-up a problem of stochastic optimal
control. The key idea of Tree-Based MPC is to transform the ensemble into a tree. A tree
represents how uncertainty spread out over time. This approach delays decisions until the
moment when uncertainties are solved and makes the control adaptive to the considered
scenarios.
38
Suspended sediment discharge distribution at tidally affected river
bifurcations
M.G. Sassi1,*, A.J.F. Hoitink1,2, and B. Vermeulen1
1 Hydrology and Quantitative Water Management Group, Wageningen University, The
Netherlands 2 Institute for Marine and Atmospheric Research Utrecht/IMAU, Utrecht University, The
Netherlands
* Presenting author Channel junctions in delta channel networks distribute water and sediment discharge over
downstream channels, affecting delta morphology and aquatic ecology. In tidal regions, flow
division at bifurcations is complicated by tides that intrude through the mouths of
distributaries, and through tidal channels connected to the fluvial system. Tides can therefore
affect the distribution of suspended sediments over downstream channels. This contribution
aims to characterize and understand the local dynamics of water and sediment discharge
distribution at river bifurcations affected by tides.
Field measurements were conducted using a shipborne ADCP in the Mahakam delta, East
Kalimantan, Indonesia. Transects spanning thirteen hours at bifurcating branches were
navigated at two bifurcations during spring tide and neap tide. Backscatter data from the
ADCP was calibrated with in situ water samples and with optical measurements from an Optical Backscatter Sensor (OBS) and a Laser In Situ Scattering and Transmissometer (LISST), to yield Suspended Sediment Concentration (SSC). Here we exploit the ability of ship-mounted ADCPs to resolve spatial and temporal variability in SSC, which in combination with flow velocity yields estimates of suspended sediment discharge. At each bifurcation, flow division drives secondary flow fields that feature a secondary flow cell induced by curvature. Velocity profiles of the along channel velocity component follow a logarithmic distribution with depth, with maximum velocities exceeding 1.5 m/s. Temporal variations in SSC are primarily controlled by the semidiurnal tide, with concentrations below 20 mg/l during high water and up to 180 mg/l during low water. Spatial distributions at bifurcating branches vary at each bifurcation, showing higher concentrations near the banks. Concentration profiles follow a Rouse-type distribution with depth. We inferred spatial-temporal distributions of settling velocity from concurrent profiles of velocity and concentration, using calibrations based on LISST measurements. In general, settling velocity estimates show a strong correlation with flow strength, which can be attributed to tidal resuspension. In one of the two bifurcations subjected to study, the division of water and suspended sediment discharge per unit width differs significantly between the two bifurcates, throughout the entire tidal cycle. In the other bifurcation, the division of water and suspended sediment per unit width is less asymmetrical, and depicts crossovers from one channel to the other in time. These crossovers consistently occur as follows: for low discharges a relatively larger share goes to the northern branch and for high discharges a larger share goes to the southern branch. The distinct behavior between the two field sites cannot simply be explained from differences in geometric properties between the bifurcations. The observations suggest that transient upstream conditions generating secondary circulations assert a strong control on the distribution of water and sediment discharge at tidally affected river bifurcations.
39
Future longitudinal dams in the Dutch Rhine
Schoor, M.M.1, Koning, R. de 2, Liefveld, W.3, Hemmen, F. van 4, Eerden, H.1
1 Rijkswaterstaat Oost Nederland, P.O. Box 9070, 6800 ED The Netherlands
phone: +31/6/22788123; fax: +31/26/3688678; e-mail: [email protected] 2 Robbert de Koning Landschapsarchitect BTN
3 Bureau Waardenburg. 4 Ferdinant van Hemmen, Landschapshistorische Producties
The Dutch flood protection programme Space for the River exists of 39 projects along the
Rhine river, for instance dike relocations, floodplain excavations and lowering of 750 groynes.
It became clear that the morphological effects of the lowering of the groynes could have
severe effects on the navigation channel. Due to the increased discharge through the groyne
fields at intermediate and high water levels, the current of the navigation channel is reduced
and sedimentation will take place. The importance of the Rhine river for navigation, limits the
possibilities for dredging, because dredging will hinder navigation. Also, the ecological value
of lowered groynes is negligible; it even may have negative effects on fish grounds.
Therefore, in a river stretch of 10 km, instead of lowering the groynes, there is a plan to
construct longitudinal dams in the inner bends of the river. The groynes in the inner bend
will be removed. The outer bends won’t be changed. With these dams the navigation channel
will get a width of 230 meters, instead of the current width of 260 meters. On the other side
of the dam there will be a 100 meter width side channel. The flow of water and sediment can
be controlled by dividing it over the navigation channel and the side channel. Therefore
variable open parts in the dams will be designed.
The design of the longitudinal dams is in preparation. Requirements are:
1. The water level drop by high discharge is the same as by groyne lowering
2. The morphological effect on the navigation channel and waterdepht, by lower
discharge, is positive
3. The ecological effect on reophilic species is positive
40
Self-formed braid bars in a numerical model
F. Schuurman, M. G. Kleinhans
Faculty of Geosciences, Department of Physical Geography, Utrecht University, Utrecht, PObox
80115, 3508 TC Utrecht, the Netherlands; [email protected], [email protected]
Braided rivers have highly variable bar dimensions, bar shapes and bar dynamics, as can be
seen in the Brahmaputra–Jamuna in Bangladesh and the Waimakariri in New Zealand. Our
objective is to understand the necessary conditions for the development of braid bar
morphology and dynamics, and to determine the effects of physical and non-physical
numerical settings. We look on the scale of an 80 km river reach and on the scale of individual
bars.
We used the two-dimensional morphological model Delft3D to produce braid bar patterns.
This model solves quasi-3D flow including near-bed secondary flow due to streamline
curvature, sediment transport including effects of transverse slope, and mass conservation of
sediment. We consider our physics-based nonlinear numerical model complementary to field
studies and experiments.
We search for the simplest possible initial situation and least amount of boundary conditions
that reproduce realistic braid bars, in order to identify what physics and boundary conditions
are required. We used different values for grid resolution, transverse bed slope effect and
perturbation, and different sediment transport formulas. Also, we identified the difference in
braid bar shape and dynamics between 2D depth averaged flow and 3D flow in a sigma grid.
Model runs were started from a plane bed with dimensions and constant boundary
conditions based on an empirical channel pattern stability diagram. A small random
perturbation is added to the upstream discharge partitioning across the inflow boundary
(0.5%) and on the initial bed level (0.1 m).
Our results show the reproduction of the essential features of real braid bars including
planform shape, length/width ratio, interaction between compound and unit bars, and
bartails (seen as ‘wings’ on both downstream sides). The conditions are sufficient to produce
realistic bar patterns. Regardless of the settings, initially, relative small sized bars with a high mode (mode 7-8) develop in the entire reach, which advect out of the model. At the same time,
relatively high bars (80% of the mean waterdepth) are initiated upstream, migrating
downstream and gradually occupying the entire reach, whilst bars grow and mode reduces.
Eventually a braid bar pattern with steady statistics is reached.
Furthermore, the results show that a 2D or 3D grid affects how dominating the upstream
formed bars are on the final bar pattern. Moreover, the braid bars remain more dynamic in
the 3D computations. The grid resolution has a major effect on the detailed bar shapes and
dynamics but not on the general dimensions. Moreover, the transverse bed slope strongly
affects the bar height. The formative time scale of bars is strongly related to the nonlinearity
of the sediment transport equation and the grain size. The perturbations in discharge and bed
level have minor effects. The braid bar patterns as well as channel dimensions and other
statistics are in good agreement with natural data.
We conclude that self-formed braided bar patterns in our numerical model are realistically
reproduced by using the simplest possible initial and boundary conditions. Constant
discharge, constant valley width and uniform sediment are sufficient for the formation of
braid bars. The braid bar pattern in general strongly depends on the width-depth ratio, and
the detailed braid bar shape and dynamics are affected by the model settings.
41
Performance off-line detention basins to inlet structure design
Shewanesh Segni Abawallo (1), Luigia Brandimarte (1)* and Marco Maglionico (2) (1) Department of Water Engineering, UNESCO-IHE, Institute for Water Education, Delft, The
Netherlands (2) DICAM, University of Bologna , Italy
Email contact presenting author: [email protected] Detention basin is a structural measure used to manage floods by temporarily storing a
portion of the incoming water volume into selected areas. The design of the inlet and outlet
structures is crucial for the optimal efficiency of the detention system. These structures
control the water volume transfer between the basin and conveyance channel. This work
investigates the sensitivity of flood peak reduction through an off-line detention basin to the
design characteristics of the inlet structures. The standard solution of a lateral weir and a
downstream inline structure is analyzed. The response of the efficiency of the basin is studied
by varying the design characteristics of the different inlet components: elevation and length
of the lateral weir and elevation, location and type of inline structure. The response of the
detention basin to the different inlet layouts is evaluated by means of three performance
criteria, two at the detention basin section and one at a downstream control section.
Laboratory data available for the detention basin under implementation on the Navile
channel (Bologna, Italy) were used to calibrate a 1D numerical model in steady state
conditions. The calibrated model was then used in simulating the mentioned different inlet
alternatives in unsteady state to determine the most influencing layout characteristics on
efficiency. The results of this study can provide general guidelines for the design of the inlet
structure of an off-line detention basin having similar structural components.
42
Questions from the Dutch Delta: Morphological modeling of the tidal river
Robin van der Sligte, Deltares
P.O. Box 177 2600 MH Delft, The Netherlands In the Rhine-Meuse Delta, the morphology of the river branches is subjected to the interplay
of two distinct hydraulic forces. From upstream on average 200 m3/s from the river Meuse
and 2000 m3/s from the river Rhine enters the system with yearly peaks of 2000 m3/s and
7000 m3/s, respectively. During its course to the sea the water movement will be increasingly
affected by the ongoing tide originating from the North Sea. Whereas in the inlands the tide
can be neglected, closer to sea the tidal swing is capable of flipping the sign of the flow
velocity fields in some of the major river branches. All of these water movements work on the
sediments of the riverbed, the resultants of which we perceive, in aggregated form, as
structures like migrating dunes, local shoals or deep pits.
The recent event of the closure of the Haringvliet estuary branch by means of a dam (1970)
had, and still has, a strong impact on the water movement in the delta. These altered
hydraulic conditions are redirecting, damping and amplifying the bed phenomena. Although
most of these new structures are harmless or impeding at worst, some developing deep pits
are damaging constructions such as groins, quays, tunnels, pipelines, and potentially
destabilizing riverbanks.
Besides adequate monitoring and reinforcements of the affected locations, the Dutch
government initiated and provides the means for improved understanding of these
phenomena. From these studies it was concluded that the phenomena like the coming into
existence and development of a local scour can only be modeled by means of a bookkeeping
layer approach for subsoil schematization, non-uniform sediment fractions (sand and mud),
capacity-reduction transport modeling for fixed layer schematization and both tidal and
river-discharge boundary conditions (Sloff et al., 2011).
For the practical application, in which both large scale (from Lobith to Hoek van Holland) and
long time (decades) simulations have to be performed the combination of tidal and river-
discharge is problematic due to the high computational load.
An important technique to reduce computation time is the use of a morphological factor. All
bed changes during a computational time step are multiplied by this factor. The resultant bed
change represents the bed change of the time step times the same factor. The technique of the
morphological factor works when the morphological change induced by the water movement
does not substantially affect the water movement itself. This substantial effect on the water
movement has to be interpreted as a change in water movement which would give a different
morphological response.
However, when tidal movements are involved it becomes clear that amplification also implies
a morphed tidal wave. Due to absorption of the wave energy by flooding of river dykes or
filling of neighboring pools, the reach of the tide is reduced and the effect near the
downstream boundary unrealistic. This unrealistic damping puts a major limitation on the
amplification level and thereby increases computational time.
A second drawback to the incorporation of tides is the incompatibility with the quasi-steady
approach commonly used in non-tidal river simulations. In order to use the technique of
quasi-steady computations, a parameterization of the morphological effect of the tidal wave
must be performed. For rivers dominated by river discharge and with minor tidal influence,
43
this parameterization can be carried out by a spatially-dependent sediment transport
amplification. However, adequate for medium tidally influenced rivers, it is yet unknown how
this technique will perform in tidally dominated river sections. It is therefore clear, that more
research has to be performed to answer these problems arising from the tidal rivers in the
Dutch Delta Reference Sloff, C.J., Van Spijk, A., Stouthamer, E., Sieben, A., 2011, Understanding and managing the
morphology of Rhine Delta branches, incising into sand-clay deposits. In River, Coastal and
Estuarine Morphodynamics: RCEM2011
44
Options for adaptation to climate change for the Rhine Meuse Delta
N. Slootjes MSc – Deltares, P.O. Box 177, 2600 MH Delft, The Netherlands, +31 88 3358080
J.W. Stijnen Phd – HKV consultants, P.O. Box 2120, 8203 AC, Lelystad, The Netherlands, +31 32
0294239
A.B.M Jeuken Phd – Deltares, P.O. Box 85467, 3508 AL Utrecht, The Netherlands, +31 88 335
7715
The Rhine Meuse delta in the Netherlands is one of the most urbanized areas in the world.
The area is densely populated, and highly utilized by various cities, ports, industry and
infrastructure. One of the major challenges for water management in this region will be
climate change. Adaptation measures to a rising sea level, increasing winter floods and
summer droughts are necessary, but at the same time spatial developments cope with an
increasing population and an economy demanding high-level agriculture and good
accessibility of harbours and waterways. A big question therefore, is how this region will
respond to ever-increasing pressure from rising seawater levels, river discharges and
precipitation during this century?
This paper presents the key results in terms of hydraulics as part of a study for the Dutch
Delta Programme (www.deltacommissaris.nl) and has been used as input for a cost-benefit
analysis.
Figure 1 Rhine Meuse Delta and its primary water defences (HKV Consultants, Sendra Design
Studio).
In this study, design high water levels are used as a safety standard. Considering climate
change over the next 100 years, it turns out that the design water levels increase throughout
the whole area of the Rhine Meuse Delta. Sea level rise is the most dominant factor in the
increase of the high water levels.
The paper considers the hydraulic implications of four ‘first generation’ adaptation strategies
and three sub-strategies to cope with the effect of climate change. These first generation
adaptation strategies have been developed to investigate extreme possibilities and are based
on the use of barriers in favour of dike strengthening measures.
One of the adaptation strategies is to decrease the failure probability of the Maeslant barrier
to 1/1000 for each closure. This gives significantly lower design water levels around
Rotterdam
Dordrecht
45
Rotterdam. The "Closeable-but-open" strategies, in which barriers are located to the East and
South of the urbanised area, have positive impact on the design water levels around
Dordrecht. But this strategy also results in backwater on the Boven-Merwede and Waal east
of the barriers. This increases the climate challenge for this area.
A "Closed-off" system in which the area around Rotterdam and Dordrecht is closed off by
barriers has the same effects as the "Closeable-but-open" strategy. The highly urbanised area
is protected, but the challenge for the upper river system and Haringvliet and Hollandsch
Diep is large. One of the sub-strategies of "Closed-off", in which the New Waterway is closed
off by a dam combined with additional retention in lake Grevelingen, shows on average the
highest reduction of the design water levels.
An "Open" strategy in which all current storm surge barriers are removed increases the
design water levels in the Southern part with a factor or two.
46
Substrate geology affecting local erodibilty in the bed of the River Lek
(Rhine delta, The Netherlands).
Esther Stouthamer1, Harm Jan Pierik1, Kim Cohen1,2
1Utrecht University, Faculty of Geosciences, Dept. of Physical Geography, P.O. Box 80.115, 3508
TC Utrecht. 2Deltares, Afd. Toegepaste Geologie & Geofysica, P.O. Box 85467, 3508 AL, Utrecht.
E-mail address corresponding author: [email protected] Localised erosion of the bed of the River Lek forms a potential risk for bank and dike stability
of this managed river. We mapped the geology and parameterised the geology of the Lek
channel belt, its banks and its substrate. We used this as input for bank failure and erodibility
calculations. This allowed predicting critical shear strength for a range of lithologies and
states of compaction and consolidation, reported in Stouthamer et al. (2011) and in this
abstract.
Erodibility for various strata in the subsurface
The channel belt of the Lek besides areas of Holocene delta peats and clays, in places dissects
the sand bodies of older channel belts and lake fills and buried eolian dunes (Table 1). This
causes bank and bed erodibility and risk for bank failure to vary locally. In the case of the Lek,
there is sufficient geological data available to predict local erodibility. Comparing geological
maps and cross-sections with multibeam imagery of the bed confirms a close relation
between substrate erodibility and the occurrence of local scour pits. New maps and sections
visualise this for the entire Lek. Especially in downstream reaches, it is the composition of the
lower part of the Holocene wedge (with local lake fills) and the presence of buried dunes that
affect erodibility locally. In the upstream reach Pleistocene subcrop and subrecent channel
belts affect erodibility locally.
For clay and peaty strata, bank erosion can occur as abrasion and as plucking. Critical shear
strength (τc) and associated critical flow velocity (uc; defined over the depth to the
outcropping layer) were calculated using the equation of Hoffmans and Verweij (1997) for
abrasive erosion. For peat and soft, relative unconsolidated clay encountered 3-12 m below
water surface, typical uc is 0,5 m/s and τc is 1,8 Pa; for consolidated clay below the active bed
at greater depths: 1,2 m/s, respectively 10,1 Pa (Table 1). Critical shear strength for
erodibility by plucking was calculated using cone penetration test (CPT) data, as a function of
resistance (CPT-R; from database) and load factor (CPT-Nk; 10 for soft clay and peat, 20 for
consolidated clay; Begemann, 1965). As a remark, applying these values to peat is a first
approximation only, as it does not account for additional variation in structure and degree of
compaction for peat of varying botanic composition. Lake fill clays are more sensitive to
plucking erosion than normal floodbasin clays. For sandy strata, τc is based on median grain
size and the Shields parameter (Zanke 2003). Risk of bank failure for loose packed sandy
strata was evaluated by evaluating relative density (Re) using the Baldi-equation, using CPT-R
and weight of bank overburden as input. In general, along the Lek risk of bank failure below 3
meters water depth is low (Re > 66%), with a few localised exceptions where risk is
‘moderate’ (33% > Re > 66%).
47
Table 1 Critical shear strength for geological strata dissected by the Lek.
Substrate
composition:
Sandy strata
Critical
shear
strength
Substrate
composition:
Clay, Peat, Loam
strata
Critical shear strength
By
abrasion
By
plucking
(Pa) (Pa) (kPa)
Holocene Holocene
Lek Channel belt
sand
0.308 Levee sandy clay loam 84
Older Channel belt
sand
0.308 Flood basin clay 1.8 79
Lake fill sand 0.218 Flood basin humic clay 75
Flood basin peat 81
Flood basin lake fill
clays with sandy
intercalations
47
Pleistocene Pleistocene
Buried dune sand 0.308 Floodplain Clay 10.1 58
Top of braid belt
sands
0.218
References
Baldi, G., Bellotti, R., Ghionna, V., Jamiolkowski, M. & Pasqualini, E. (1986). Interpretations of
CPT’s and CPTU’s, 2nd part: Drained penetration of sands. 4th International conference on
field instrumentation and in-situ measurements, Singapore, 143-156.
Begemann H. (1965). The friction jacket cone as an aid in determining soil profile. Proc. 6th.
In. Conf. SMFE.
Hoffmans, G.J.C.M. & Verheij, H.J. (1997). Scour manual. Balkema Rotterdam.
Stouthamer, E., Pierik, H.J., Cohen, K.M. (2011). Erodibiliteit en risico op zettingsvloeiing als
maat voor stabiliteit van oevers, onderwatertaluds en rivierbodem van de Lek. Deelproject
rapportage ‘Verkenning beheer Bodemligging Lek’, Universiteit Utrecht / Deltares. 49 pp.
September/October 2011.
Zanke, U.C.E. (2003). On the influence of turbulence on the initiation of sediment motion, Int. J.
Sediment Res., 18(1), 1– 15.
Acknowledgement
This work is part of a Rijkswaterstaat commissioned project ‘Verkenning beheer
bodemligging Lek’, aiming to improve management of morphological development of the bed
of the embanked River Lek. The project is carried out by Deltares (Unit ZWS; project nr:
1204817), Utrecht University and DHV.
48
Uncertainty in bio-geomorphological assessments of lowland river
floodplains resulting from landcover classification errors
Menno Straatsma1,7, Marcel van der Perk2,6, Aafke Schipper3,6, Reinier de Nooij4, Rob Leuven3,6,
Fredrik Huthoff5, Hans Middelkoop2,6.
1 Department of Earth System Analysis, Faculty of Geo-Information Science and Earth, Twente
University,
[email protected], tel. +31 (0)53 4874245 2 Faculty of Geosciences, Department of Physical Geography, Utrecht University,
3 Radboud University Nijmegen, Institute for Wetland and Water Research, Department of
Environmental Sciences 4 Optimal Planet training and consultancy
5 Water systems modelling, HKV Consultants 6 NCR, Netherlands Centre of River Research, Delft, The Netherlands
7 Corresponding author Landcover maps provide essential input data for a sequence of models used to quantify the
hydrodynamics and ecology of lowland rivers and their floodplains. Hydrodynamic models
provide estimates of peak water levels and sediment deposition while ecological models
characterize habitat suitability, biodiversity (Lenders et al., 2001; Schipper et al., 2008) and
ecosystem services (Nelson et al., 2009). Such models are routinely used in the
environmental impact assessment of landscaping measures that aim to reduce the flood risk
and improve the ecological quality of the river area (Van Stokkom et al., 2005; Samuels et al.,
2006). In general, however, the impact of landcover classification errors on hydrodynamic
and ecological model output has hardly been quantified. Our main objective is to assess the
uncertainty in biogeomorphological modeling of a lowland river depending on the
classification accuracy of landcover maps.
We quantified this uncertainty for the three distributaries of the river Rhine in The
Netherlands with respect to four aspects: (1) flood water levels using WAQUA, (2) annual
average suspended sediment deposition using SEDIFLUX (Middelkoop and Van der Perk,
1998), (3) potential biodiversity values using BIOSAFE (De Nooij et al., 2004), and (4)
ecotoxicological hazards based on a food web after Schipper et al. (2008). We assessed how
the outcomes of these quantitative models depend on the classification error of the input
landcover maps in a Monte Carlo analysis. The uncertainty was assessed for two overall
classification accuracies:f 69 and 95%. For each classification accuracies, we generated 15
land cover map. Subsequently we ran all four models with the 30 realizations.
The error in the land cover map gave an uncertainty in water levels of up to 20 cm. Overbank
sediment deposition varied up to 100% in the area bordering the main channel, which is
directly linked to the variations in flow velocity encountered in the same area. However,
when aggregated to the whole study area, the 68% confidence interval in sediment
deposition was only 0.6%. The ecotoxicological effects, indicated by the fraction of little owl
habitat with a daily cadmium intake exceeding a toxicity threshold of 148 μg d-1, varied
between 16 and 19% for the Nederrijn-Lek, 39 and 42% for the Waal, between and 54 and
60% for the IJssel. A classification accuracy of 69% in the land cover map resulted in
significantly higher potential biodiversity values in comparison with an accuracy of 95%. The
magnitude of the overestimation of biodiversity values at low classification accuracies
remarkably differed for various protected species and between river distributaries.
49
Compared to biogemorphological effects of landscaping measures, the effects due to the
uncertainty in the land cover map are of the same order of magnitude. Given high financial
costs of these landscaping measures, increasing the classification accuracy of landcover maps
is a prerequisite for improving the assessment of the effectiveness and efficiency of
landscaping measures.
References
De Nooij, R.J.W., Lenders, H.J.R., Leuven, R.S.E.W., De Blust, G., Geilen, N., Goldschmidt, B.,
Muller, S., Poudevigne, I., Nienhuis, P.H., 2004. BIO-SAFE: assessing the impacts of physical
reconstruction on protected and endangered species. River Research and Applications 20,
299-313.
Lenders, H.J.R., Leuven, R.S.E.W., Nienhuis, P.H., De Nooij, R.J.W., Rooij, V., 2001. BIO-SAFE: a
method for evaluation of biodiversity values on the basis of political and legal criteria.
Landscape and Urban Planning 55, 121-137.
Middelkoop, H., Van der Perk, M., 1998. Modelling spatial patterns of overbank sedimentation
on embanked floodplains. Geografiska Annaler 80 A, 95-109.
Nelson, E., Mendoza, G., Regetz, J., Polasky, S., Tallis, H., Cameron, D., Chan, K.M., Daily, G.C.,
Goldstein, J., Kareiva, P.M., Lonsdorf, E., Naidoo, R., Ricketts, T.H., Shaw, M., 2009. Modeling
multiple ecosystem services, biodiversity conservation, commodity production, and tradeoffs
at landscape scales. Frontiers in Ecology and the Environment 7, 4-11.
Samuels, P., Klijn, F., Dijkman, J., 2006. An analysis of the current practice of policies on river
flood risk management in different countries. Irrigation and Drainage 55, S141-S150.
Schipper, A.M., Loos, M., Ragas, A.M.J., Lopes, J.P.C., Nolte, B., Wijnhoven, S., Leuven, R.S.E.W.,
2008. Modeling the influence of environmental heterogeneity on heavy metal exposure
concentrations for terrestrial vertebrates in river floodplains. Environmental Toxicology and
Chemistry 27, 919-932.
Van Stokkom, H.T.C., Smits, A.J.M., Leuven, R.S.E.W., 2005. Flood defense in the Netherlands a
new era, a new approach. Water International 30, 76-87.
50
A New suit for the IJsselmeer
Possibilities for facing the future needs of the lake by means of an optimized dynamic
target water level
Master Thesis by Jan Talsma
TUDelft/Deltares
0647215276 / 0883358538
The IJsselmeer is located in the center of the Netherlands. Because of its relevance for the
Dutch economy and society, it is often addressed as the Wet Heart of the country.
Furthermore, being the collector of part of the water of the Rhine, the future management of
the IJsselmeer will strongly influence river management issues in the region, in order to tune
the water supply as required. When looking into the future, the IJsselmeer is under climate
threats. Wetter winters will bring more water into the system, in combination with sea level
rise, and lower gravity discharge to the Waddenzee. This will generate safety issues. On the
other hand, summers will be drier, putting the satisfaction of water demand in danger.
The goal of the research is to define a dynamic target water level for the IJsselmeer which is
variable through the whole year by means of an optimization approach. The optimization
uses a single objective function considering dike safety and water demand. However, when
management measures alone are not enough to define a climate-proof IJsselmeer, extra
measures are taken into consideration: namely a pumping station at the Afsluitdijk and early
storage in March.
The main research question asks for an evaluation of the optimization methodology used to
define efficient alternatives for the IJsselmeer. The sub-question requires the assessment of
the flexibility of the target water level in the IJsselmeer towards a climate-proof system, and
the definition of extra measures, when needed.
The definition of the optimum measures is achieved in several steps. First, the objective of the
problem owner is defined. The Dienst IJsselmeergebied is defined as the problem owner with
interests in safety and water demand satisfaction. Then indicators are derived from the
objectives, and merged into the objective function. Classes of measures are selected, and a
model of the system is designed for their evaluation. Finally, the optimization problems are
defined in order to design the optimum alternatives.
The research showed that a different planning of the target water level alone is not able to
satisfy the needs of safety and water demand in the long term. As it is now, the IJsselmeer is
flexible in the short term, but extra measures are needed for a climate proof system in 2050
and 2100. A pumping station at the Afsluitdijk is an effective measure to guarantee safety for
all the scenarios, but other possibilities might be interesting as well. Early storage in March is
effective in the medium horizon (2050) but need high target water levels along the summer
for the long term (2100). This might generate safety issues.
Even if applied on a simplified case, the use of an optimization methodology manages to
define a realistic picture of the flexibility of the IJsselmeer, and retrieves efficient options for
possible future strategies. For this reasons, the present research can be considered a
successful implementation of an optimization approach for the IJsselmeer.
51
A more extensive and detailed optimization tool should be realized for the IJsselmeer, in
particular it is recommended to use a multi-objective analysis and include costs in the
definition of the indicators.
52
Tracking the uncertainty in streamflow prediction through a hydrological
forecasting system
Trang Van Pham
Department of Water Engineering and Management
University of Twente
Contact address: Trang Van Pham, Email: [email protected] A flood forecasting system is a complex system which consists of many different components
and each of these components can contain, to some extent, an uncertainty. Studying the
uncertainties in flood forecasting, quantifying and propagating them through the system can
help to gain more information about the different sources of uncertainty that may affect the
forecasts. This information can later be added to the forecasts to improve their quality. These
issues bring several challenges to the study of flow forecasting uncertainty: firstly, what is the
impact of different sources of uncertainty on the quality of flood? Secondly, forecasts among
all sources of uncertainty that stem from different components of the system, which sources
significantly affect flood forecasts? Thirdly, which methods can be used to efficiently quantify
and propagate those uncertainties through a forecasting model? Finally, which measures
should be used to evaluate the uncertainty quantification and their impact on the quality of
the forecasts? The aims of this research is to quantify and propagate the different kinds of
uncertainty sources which play a role in flood forecasting; and to investigate methods to
assess the quantified uncertainties and proper measures to evaluate the uncertainty
quantification.
In this research, the GRPE forecasting system, an ensemble prediction system based on the
lumped GRP hydrologic model, is applied to three catchments in France. The uncertainties
from precipitation data (input precipitation which is used for flow simulation and forecast
precipitation used for flow forecasting), hydrological initial conditions (discharge data) and
model parameters, which are acknowledged as important sources of uncertainty in
hydrological modelling and forecasting, are studied. They are individually quantified and then
propagated together through the forecasting system with an experimental approach by
multiplying the simulations. The model structure uncertainty is not considered in the scope
of this research.
Methods for uncertainty quantification are defined and applied to each source of uncertainty.
Two ensemble prediction systems from ECMWF and Météo-France are used to account for
the forecast precipitation uncertainty for lead times from 1 to 9 days. For the uncertainty of
input precipitation data, geo-statistical simulations of spatially averaged rainfall, conditioned
on point data, and available for one study catchment, are chosen to provide the multiple
statistical realizations of daily spatial rainfall fields over the study area. The hydrologic initial
condition uncertainty is quantified by using an ensemble of discharges to update the state of
the routing reservoir of the forecasting model. These discharges are retrieved from the
analysis of uncertainties affecting the rating curves of each study catchment. Ten different
periods of data, with the length of 5 years each, are selected to calibrate the model and thus to
account for calibration period uncertainty. Finally, the Generalized Likelihood Uncertainty
Estimator (GLUE) method is alternatively used to quantify the parameterization uncertainty.
This is done by taking a large number of 125.000 sets of parameters to find the confidence
intervals. To assess the results of uncertainty quantification, two probabilistic evaluation
measures, the Brier (Skill) Score and the reliability diagram, are employed. In addition,
confidence intervals of the forecasts are used to visualize the outcome of the research.
53
The results show that input precipitation uncertainty does not have noticeable impact on the
forecast output. This may be due to the method used to quantify the uncertainties from this
source, which may be inappropriate to correctly capture them. For the catchments studied,
this source of uncertainty can, therefore, be neglected when propagating different sources of
uncertainty through the system. The other sources of uncertainty show large impacts on flow
forecasts. Initial condition uncertainty shows large impacts for small lead times (up to 2 days).
After that, forecast precipitation uncertainty has the largest impact; this impact is more
significantly pronounced at high lead times. Depending on the catchment, parameter
uncertainty can have more impact if it is evaluated from the variation of the calibration
period or from the GLUE method.
Based on the results of this research, and on the catchments and methods investigated, it is
recommended to take into consideration the uncertainty of forecast precipitation, initial
condition and model parameters in flood forecasting. There are different ways to account for
parameter uncertainty, but the proposed approach of using different calibration periods
proved to be a simple method but able to improve the quality of the forecast outputs.
54
Measuring profiles of turbulence quantities with two coupled ADCPs in
geophysical surface flows
B Vermeulen1, MG Sassi1, AJF Hoitink1,2
1Hydrology and Quantitative Water Management Group
Department of Environmental Sciences
Wageningen University, PO Box 47, 6700AA Wageningen, The Netherlands 2Institute for Marine and Atmospheric Research
Department of Physical Geography
Utrecht University, PO Box 80.005, 3508TA Utrecht, The Netherlands Understanding turbulence is vital to future progress in the hydrodynamics and
morphodynamics of rivers, estuaries and the coastal ocean. Turbulence strongly controls
exchange of momentum heat and suspended or dissolved matter in geophysical surface flows.
Acoustic Doppler current profilers (ADCPs) offer a relatively new way of analyzing
turbulences. Existing methods used to determine Reynolds stresses from ADCPs often rely on
assumptions about turbulence anisotropy and require perfect vertical alignment. Since the
ADCP measures velocity components in different locations in space it is not possible to
directly combine raw measurements of velocity components from different acoustic beams to
obtain terms in the Reynolds stress tensor. A widely used method to determine some of
these parameters is the so-called variance method. This method consists of first determining
the variance in velocity in the raw velocity components. Afterwards these components are
combined to obtain terms in the Reynolds stress tensor. Unfortunately assumptions are
necessary since it is not possible to solve the six independent terms in the Reynolds stress
tensor with only three or four beams from a single ADCP.
We introduce a new technique to measure profiles of each term in the Reynolds stress tensor
using coupled acoustic Doppler current profilers (ADCPs). The technique is based on the
variance method which is extended to the case with eight acoustic beams. All the terms in the
Reynolds stress tensor can now be solved explicitly. We show which mounting configuration
is preferable and how errors propagate depending on the spatial orientation of the
instruments and how this translates into minimum detectable stresses. We apply the
technique successfully to data collected in the Mahakam River, East Kalimantan, Indonesia.
Data was collected in a tidally influenced river bend. Profiles of normal and shear stresses
resemble typical profiles for curved channels with upflow and downflow. The results show
standard assumptions about turbulence anisotropy, often used in the conventional method,
to hold only to a limited extent.
55
Real-time control of a water system the size of Holland (Jiangsu, China)
Meinte Vierstra, Delft University of Technology
China is currently working on the construction of the massive South-North Water Transfer
Project (SNWTP), the largest project of its kind ever undertaken (transfer of 44.8 billion m3
of water per year; over 300 million expected benefiting people). The project corresponds to
China’s severe water scarcity and geographically uneven south-north distribution. The
'Jiangsu water transfer system' is a 411 km long section of this project and will divert as much
as 8.9 billion m3/year (up to 500 m3/s ) from the lower Yangtze River reach uphill through
an existing network of canals and lakes in the direction of the Yellow River and Beijing. In
order to fulfill these functions, controllable structures, such as gates, weirs and pump stations
are used.
Real-time control (i.e. daily management) of such a complex water system with multiple,
conflicting objectives is preferably done by an advanced controller such as Model Predictive
Control (MPC). In this thesis MPC is developed for the Jiangsu water transfer system and the
performance is assessed. MPC is a control algorithm that makes explicit use of a simplified
process model (internal model) of the real system to obtain control actions by minimizing an
objective function over a prediction horizon. In order to put the performance of MPC into
perspective, classical control [Proportional-Integral control (PI)] has been developed for
comparison in the test scenarios.
The research showed that the complex Jiangsu water system can be modeled using a 1D-
hydraulic model(SOBEK) and can successfully be controlled using MPC. The results show that
MPC outperforms classical PI control under all scenarios. MPC keeps water levels within a
bandwidth of 0.16 meters from target level under all circumstances and therefore never
exceeds minimum or maximum allowed water levels. The higher the flows through the canals,
the larger the water level deviations. With good disturbance predictions (e.g. precipitation
forecasts and water usage by horticulturists) the performance of MPC on water levels is
further improved. MPC is not able to significantly reduce operational costs without making
sacrifices on other objectives.
In this research a time step of 1 hour and a prediction horizon of 2 days have been used. By
using a 64-bit, quad core computer with a commercial solver (TOMLAB) the calculation times
have proven to be sufficiently short for real-time application. This shows that it is possible to
successfully control a water system the size of Holland with MPC.
It is recommended to do further research by testing MPC parallel to the real water system
and compare the performance to current control. Furthermore it is desirable to develop a
user interface that allows water managers to simply implement different control objectives.
56
Numerical investigation for characteristics of hyperconcentrated flood
propagation
Wei Li, Zhengbing Wang, Huib J. de Vriend
Department of Hydraulic Engineering, Faculty of Civil Engineering and Geosciences,
Delft University of Technology,P.O. Box 5048, 2600 GA Delft, the Netherlands Unlike low sediment-laden flow, hyperconcentrated flow sometimes exhibits abnormal
features. For instance, the peak discharge of hyperconcentrated flood could increase
dramatically with negligible tributary contributions when propagating downstream. Yet, the
reason for the occurrence of this peculiar phenomenon is still far from clear because of
contrasting explanations by previous studies. In this paper, we intend to reveal the
mechanism of the issue by means of numerical modeling. The strong interactions of flow,
sediment, and river bed in hyperconcentrated flow are tackled with coupled approaches in
the current model. Preliminary results demonstrate that for a single channel without
floodplains, the reduction of channel storage during bed erosion could contribute to the
downstream increasing peak discharge by amplifying the turbid flow volume. Besides, the
reduction of flow resistance in high sediment concentration could also interpret this issue.
The propagation of flood wave accelerates when flow resistance decreases with increasing
sediment concentration, thus the overlap of successive flood waves may occur in the
downstream causing enlarged peak discharge. Further study of complex channels with
floodplains is the way forward.
Figure 1 Time evolution of (a) flow discharge, (b) change of water level and (c) change of
channel storage
57
Dynamic modeling: social and physical interactions to explore future
water management
Nanda Wijermans, Marjolijn Haasnoot and Hans Middelkoop
Water management is part of a complex system wherein policy makers respond to natural
and social states and events. Apart from being affected, policy makers have a strong effect on
the water system via their measures, such as dike raising. This results in a continuous
interaction between the physical river system and water-management.
To support long-term water-management, our approach is to explicitly include these
dynamics and interactions in an integrated physical-social model that is used to develop
strategies for coping with uncertainties about the future. Present water policy studies mostly
include climate scenarios and sometimes socio-economical scenarios at one or two points in
the future; however they neglect the continuously adapting role of policy makers.
Concerning this social uncertainty of policy decision-making, our approach is shaped in two
ways: 1) to include real policy-makers in a serious game (participatory simulation) and 2) to
embed a model of policy decision making in interaction with a simulated water system (social
simulation). In the participatory simulation real policy makers are included to embed social
uncertainty. The policy makers act from their own role in an imposed reality based on the
Dutch delta program structure and decision-making issues while time proceeds and physical
and societal circumstances change. In the social simulation on the other hand, the social
uncertainty of policy decision-making is computationally represented by artificial policy
makers, i.e. agents. These agents respond to a changing context given their own role and
incentive. Their behaviour is described in the form of rules that will be derived from theory,
previous games and analysis of the Dutch delta programme.
Both the participatory simulation as the social simulation approaches result in measures that
change the water system, which in turn affects the policy makers etc. The water system is
represented by a hydrological meta-model that produces water and economical impacts
through time based on the current state of the water system, natural variability, climate and
socio-economical scenarios. The resulting interaction between the water system and the
social system produce a sequence of measures and system states over time; they form a
pathway to the future (see figure 1, next page).
58
The generation and evaluation of these pathways allow for a process view on the effect of
measures including both physical and social uncertainties. The process view taken in this
project allows for systematically exploring the dynamics of a system that changes during time
in which both it’s social and physical components have their own dynamics and interact with
each, i.e. a complex system. This inclusion of both physical and social uncertainties in
combination with a process view allows for developing sustainable strategies that can cope
with a variety of futures.
Figure 1 Pathway to the future is a result of the interaction between the physical
system and the social system during time. Herein is the system state affected by
context (described in a climate and socio-econical scenario) and the subsystems is
consists of (physical and social system interaction).
59
Risk-based control of external salt water intrusion for the Rhine-Meuse
Estuary
Marit Zethof, Delft University of Technology, Faculty of Civil Engineering and Geosciences, Delft,
the Netherlands; HKV Consultants, Lelystad, the Netherlands
It is necessarily to pay more attention to the future fresh water supply, due to the predicted
effects of climate change in the Netherlands. More frequent salt water intrusion during the
summer semester is caused by the joint occurrence of low river discharges and the expected
sea level rise. The control of external salinity is necessary to guarantee a sufficient water
quality of the main water system and so protect the fresh water inlets from the intruding
saline water. Consequently, regional water systems are able to take in fresh water of the main
water system to control internal salinity, through counteracting salt seepage by means of salt
flushing.
The control of external salinity can be realized by the implementation of measures that
interfere in the main water system; e.g. by optimizing the fresh water distribution of the
Rhine-Meuse Estuary. On a regional scale, it is of main interest to guarantee the fresh water supply to the control area of Rijnland via the fresh water inlet of Gouda.3
The ability of controlling salt water intrusion in the Rhine-Meuse Estuary is examined in a
case study via a physical model simulation study. Three measures are investigated that
particularly focus on reducing the salt water intrusion into the Hollandse IJssel:
1. Krimpenerwaard route (calamity measure);
Diverting abstracted fresh water of the Lek via the Krimpenerwaard polder to
discharge a larger fresh water volume onto the Hollandse IJssel.
2. Rhine discharge redistribution (preventive measure);
Optimizing the Rhine discharge distribution over the rivers Waal and Pannerdens
kanaal by increasing the Lek discharge and reducing the Waal discharge.
3. Temporarily Spui closure (preventive measure);
Optimizing the seaward flowing fresh water volume of the Beneden Merwede via the
Noord, Nieuwe Maas and Nieuwe Waterweg towards the North Sea, by means of the
temporarily closure of the river Spui.
The alternative Krimpenerwaard route is a highly auspicious measure, since it almost totally
diminishes intruding salt water in the Hollandse IJssel and requires little adaptation of the
Dutch water system. The optimisation of the Rhine discharge distribution is very effective as
well, in case the Lek discharge will be increased with at least 10 m3/s. Unfortunately, a
reduction of the Waal discharge results in negative economical side effects for the
navigational sector. The prioritisation of available fresh water over the navigational and the
agricultural sector will always be a policy decision on a national level.
3 Rijnland accommodates three economic ‘Greenports’; i.e. bulb farming (1), glasshouse
horticulture (2) and floriculture & arboriculture (3).
60
Whether a measure will be implemented, depends on the current pursued fresh water policy.
Salinity risk management can support the governmental decision-making process, by
assessing the cost-effectiveness of each measure.
61
Effects of discharge fluctuation on morphological equilibrium of rivers
Zheng Bing WANG
Deltares & Delft University of Technology
[email protected] / [email protected] The equilibrium longitudinal profile of a river is such that the river can exactly transport the
sediment with the water from the river basin. It is thus determined by the upstream
discharge and sediment transport. For constant discharge and sediment transport the
equilibrium state is a steady uniform flow. The water depth and the bed slope can be
determined as function of the discharge and sediment transport for given river width.
However, in reality river discharge is not constant in time. An analysis is carried out how
fluctuations of river discharge with time scales much smaller than the morphological time
scale influence the longitudinal profile of a river. The results of the analysis are used to
explain the morphology of tidal rivers and offer an alternative method for the schematization
of discharge regime (seasonal variation) in morphological analysis for rivers.
62
63
Colofon
Editor:
Erik Mostert, Laurène Bouaziz (Delft University of Technology)
Design cover:
Laurène Bouaziz (Photo on cover: Laurène Bouaziz)
Number of prints:
100
Keywords:
NCR, rivers, research
To be cited as:
E. Mostert, L.J.E. Bouaziz, 2011 (eds.) NCR-Days 2011: Controlling the Dutch rivers, Book
of Abstracts
64
