(SESSION 1) Kees Bons (Deltares) Structural and Non-structural Measures

8/11/2019 (SESSION 1) Kees Bons (Deltares) Structural and Non-structural Measures

1/17

12 februari 2010

Comparing structural& non-structural measures

Kees Bons

Flood Risk Management and Urban Resilience Workshop II

May 28-29, 2013

Venue COEX, Seoul, Republic of Korea


2/17

Urban Flooding Issues

o Unplanned Urban expansion and growth into river

valleys and coastal areas

o Water supply, Drainage, Waste water and Floodprotection did not develop as fast as the growing needs

o Subsidence (due to overexploitation of GW)

o Ineffective Operation and Maintenance of flood defences,pumping stations and drains.

o Loss of natural defences (for example, mangroves)

o Climate Change? (more extremes, sea level change)


3/17

No solutions, just responses

Structural adaptation measures

(SAMs):Constructed permanent facilities to

reduce the damage risk

Non-structural adaptation measures(NSAMs):

Responses to urban water problems

that may not involve fixed or permanent

facilities. Their positive contribution to

risk reduction is most likely through aprocess of influencing behavior, usually

through building capacity in all

stakeholders through active learning

and appropriate and effective

engagement between stakeholders(Taylor and Wong, 2002).


4/17

12 guiding policy principles

1. Every flood risk scenario is different: there is no flood management blueprint.2. Designs for flood management must be able to cope with a changing and uncertain

future.

3. Rapid urbanization requires the integration of flood risk management into regularurban planning and governance.

4. An integrated strategy requires the use of both structural and non-structural measuresand good metrics for getting the balance right.

5. Heavily engineered structural measures can transfer risk upstream anddownstream.

6. It is impossible to entirely eliminate the risk from flooding.7. Many flood management measures have multiple co-benefits over and above their

flood management role.

8. It is important to consider the wider social and ecological consequences of floodmanagement spending.

9. Clarity of responsibility for constructing and running flood risk programs iscritical.

10.Implementing flood risk management measures requires multi-stakeholder cooperation.11.Continuous communication to raise awareness and reinforce preparedness is

necessary.

12.Plan to recover quickly after flooding and use the recovery to build capacity.


5/17

probability

of failure

risk

vulnerability

protection

measures

hazard map

damage

sensitivityo

risk

map

(changes in)

pressures

adaptability

hot spot map

osometimes called vulnerability or susceptibility

(changing)th

reshold

strength

protection

strategy

Flood protection measures: Result of extensive

vulnerability analysis


6/17

Measures we could take to reduce flood risk

> 200 adaptation measures identified..

SAMs: Structural (hard) measures (# >100)

Collective: e.g. dikes, drainage systems

Individual: e.g. wet or dry proofing

NSAMs: Non-structural (soft) measures (# > 100)

Collective: e.g. contingency plans, legislation

Individual: e.g. risk consciousness, insurance

and counting


7/17

Adaptation measures

Objective:Reduce vulnerabilityof urban areas by

avoiding damage

damage reduction

creating redundancy and adaptabilityfor long term, unexpected change

But what is their effect and effectivity ? (e.g. retention pond)

In everyday situation Under design conditions (T = 10-100 years)

Under very extreme conditions (T = 500>1000 years)


8/17

What if we rely only on structural measures

- When they fail they often fail dramatically (a chain is as strong asits weakest link)

- Structural measures cannot evolve with development

- Structural measures generally require high investments

- Structural measures often have major side-effects


9/17

Threshold capacity

Coping capacity

Recovery capacity

Adaptive capacity

recurrence time

Strategy to reduce/manage vulnerability

* Graaf, R. de, N. van de Giesen and F. van de Ven, 2007, Alternative water management

options to reduce vulnerability for climate change in the Netherlands, Natural Hazards nov.

Strengthen four capacities* to reduce vulnerability


10/17

Traditional Vulnerability reduction approach

First priority:SAMs to strengthen threshold capacity for fluvial andcoastal flooding

e.g. World Bank (2010) Climate risk and Adaptation in Asian Coastal Megacities

Consequences:

Other capacities and NSAMs get neglected

Increased vulnerability for other riskse.g. pluvial flooding, drought, land subsidence, heat

Lock-in

Effectivity in very extreme conditions (T>100 yr) is poor

Adaptability is limited


11/17

Vulnerability reduction approach

Conclusion:

Strengthen all four capacities

SAMs show limited adaptability

Most SAMs strengthen threshold &

coping capacity

SAMs require high federalor

regionalinvestments

NSAMs require less, localor

individualinvestments

NSAMs require study (learning) and

regular training

SAMs cant do without NSAMs


12/17

SAMs cant do without NSAMs

What would have happened

in Holland without effective flood early warning system in Indonesia with an effective tsunami warning system

in New Orleans without an effective evacuation plan

in Brisbane if their zoning plan had been water resilient

SAMS are only effective if people are aware, prepared, trained

and space use and construction are regulated

(and preparedness, rules and

regulations are maintained)

Considering all the uncertainties

the buzz word now is:

ADAPTIVE Management

NSAMS prove to be much more

adaptive than SAMS

Raise level +1.1 m in spring

Scenarios

Steam 2050

Change to drougth/salt

tolerant crops

2100

Lower navigation sluices. Increasing

pumping capacity. Strenthen dikes.

Lower inlet structures.

Raise IJsselLake level

within current infra+0.1

Decrease level within

current infra (-0.6?)

Accept navigation abstructionduring extreme drougths

Decrease level and adapt

infrastructure (-0.8?)

More water through

IJssel in summer. Afh. NWW

Adapt regional water system

infrastructure. Raise dikes.

More water to Ijssel in spring

Raise level +0.6 mRaise dikes. More water to Ijssel.

Adapt regional watersystem

infrastructure

Change land use

Current policy

More efficient water use

-0.20 - -0.4 m NAP

e.g. increase regional storage, flushing

optimalisation, flex level control. After

2050 pumping capacity needs to be

increased.

After 2050 pumping capacity needs to

be increased

Optimising current policyFlexible water levels

Watervraagbeleidsopties

Waterbeschikb

aarheidbeleidsopties


13/17

How to select an appropriate set of AMs?

Three-step approach

1: Complete vulnerability-analysis

2: Select a strategy to reduce vulnerability

3: Select appropriate set of measures

many stakeholders / many stakes

many SAMs and NSAMs

design and negotiation approach


14/17

Every situation is unique and dynamic

Type of flood (fluvial, pluvial,coastal, ground water)

Development and (spatial)

planning stage

Economic and social values

Culture and government style

Individual vs Community

Environment

0,0000

0,0002

0,0004

0,0006

0,0008

0,0010

0,0012

2000 2020 2040 2060 2080 2100 2120 2140 2160

year

probability

(1/year)


15/17

Resulting portfolio of AMs

1. Threshold capacity

Waterrobust infrastructure

Enlarged seasonal storage

High floor level vs street level

Floating housing

2. Coping capacity

Major drainage system; adapted street

profile

Wet proofing vulnerable buildings

Warm grass instead cold grasses

4. Adaptive capacity

Temporary houses & buildings

Adaptive management

Water-based spatial planningUpdates water & space policies

3. Recovery capacity

Redundant pumping capacity

Cleaning & drying capacity

Water supply capacity in extremely dryperiods

Measures to strengthen

With the varying time and adaptation horizons


16/17

Resulting designNew Orleans

Dutch Dialogues III, April 2010, www.dutchdialogues.com


17/17

Closing

Thank you for your attention!

[email protected]
mailto:[email protected]:[email protected]

Documents

(SESSION 1) Kees Bons (Deltares) Structural and Non-structural Measures