11

Hydrological processes and drainage basins:

Case study of the River Souteyran

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22

Hydrological Processes and Drainage Basins: A Case Study Of The Souteyran River

Teachers’ notes Channel processes and landforms come under close scrutiny in this unit, as does river morphology. River

morphology can usually be considered in three dimensions; long profile, cross-sectional shape and plan-

form. This unit concentrates on the changes which the Souteyran exhibits on its journey along the southern

flank of Mont Lozere to its junction with the Tarn at Pont de Montvert.

The work for this unit is carried out from the Eagle's Nest without the need for transport except for the return

journey from Le Pont de Montvert. Students walk the entire length of the River Souteyran (approx. 10km)

over rough ground and along the Stevenson’s Trail. Most groups measure between 4 and 10 sites at a

variety of locations. Liaise with your group leader before you set out on the number of sites and the

locations that you wish to study.

This study gives many opportunities for students to produce coursework based upon the data collected. A

list of possible project titles is included with this unit.

Many groups spend a good deal of time in the evening drawing out cross-sectional areas. We have

software that processes the student’s data quickly and efficiently, producing a cross-sectional diagram and

calculating discharge. This leaves groups with time for discussion and more sophisticated of the results that

they have collected. If you would like to use the software, please ask your group leader.

Some groups may choose to study variations in water quality. Because of the organic nature of the farming

in the valley, there is very little nitrate pollution and the acidic nature of the granite bedrock eliminates most

meaningful variations in pH. The most successful way of testing for changes in water quality is to look for

biological indicator species. However the ‘clean’ nature of the river means that little variation is apparent

between sites. For a more detailed investigation the Freshwater Pollution unit based upon the River Lot

should be considered.

On the walk down it is easy to see evidence of rejuvenation in the valley. This may be a useful teaching

point.

Key Specification Areas:

• The drainage basin, hydrological cycle: the water balance;

• Factors affecting river discharge: the storm hydrograph;

• The long profile – changing processes: types of erosion, transportation and deposition, types of load,

the Hjulstrom curve;

• Valley profiles – long profile and changing cross-profile downstream, graded profile, potential and

kinetic energy;

• Changing channel characteristics – cross-profile, wetted perimeter, hydraulic radius, roughness,

efficiency, and links to velocity and discharge;

33

• Landforms of fluvial erosion and deposition – potholes, rapids, waterfalls, meanders, braiding, flood

plains;

• Process and impact of rejuvenation – knick-points, waterfalls, river terraces;

• Physical and human causes of flooding – location of areas of high risk in an MEDC;

• Impact of flooding – case study of the river Souteyran;

• Flood management strategies – to include hard engineering and soft engineering.

Reference Texts

Barker, A., Redfern, D and Skinner, M. (2008) AQA AS Geography. Phillip Allen Updates.

Knighton D (1984) “Fluvial Forms and Processes”

Knill, R. and Smith, J. (2008) AQA AS Geography.

Lenon & Cleves (1994) “Fieldwork Techniques and Projects in Geography” Collins

Miller (2000) “Fieldwork Ideas in Action” Hodder & Stoughton

44

Introduction

General Information The Massif Central, a roughly triangular upland area covering one-sixth of France, contains a landscape of

enormous variety characterised by a number of distinctive landforms. Water is an important and dynamic

component of this landscape system. The striking gorges of the limestone Causses reflect the erosive power

of the Massif's principal rivers. Today these waters have become a major recreational attraction and have

brought an important source of revenue into the region.

Elsewhere, water plays a vital role in agricultural activity and many rural valley communities rely upon the

flow of rivers for their continued prosperity. The dynamic nature of the river system has a direct impact on

man. Heavy rain in October 1987 and September 1994 brought severe flooding to many areas; the droughts

of 1989 and 1990 have reduced river flow and this, together with increased deposition, has made it almost

impossible for some of the canoeing and rafting businesses to operate profitably.

People also have an impact on rivers: pollution is becoming a major problem as more farmers turn to

chemicals to increase yields and as domestic waste tips build up outside the major settlements. River

channels have been straightened and banks protected in urban areas and in the rural sector channelisation

has been used to re-direct flow onto agricultural land.

The physical geography of the Massif Central means that the region forms a vast watershed from which

rivers flow to the Mediterranean, and the Atlantic coasts. These rivers are not important for navigation but

their valleys provide route-ways for road and rail transport away from the mountain mass to other parts of

France. The water input into these river systems comes principally from the Atlantic depressions.

The Massif is well watered. Lozère has more than 2700 km of water courses and 230,000 hectares of forest

land – it constitutes “Water Tower” and green lungs of Languedoc-Rousillion to which it belongs.

Precipitation is high with more than 1,200 mm per annum being recorded in the highest areas. The whole of

the Massif has more than 75 days of frost each year and large areas of ground are snow covered for more

than two months of the year, rising to six months in the high mountains. The prevailing soil and geological

conditions favour rapid run-off and overland flow tends to be the dominant process during periods of heavy

rain (See Figure 1). This is accentuated where deforestation has occurred on a large scale. There are

many natural and artificial water stores that may help to regulate river-flow, such as Lac Villefort at Villefort

and the Reservoir de Cambous between Florac and Alès. These are used for the supply of water to

surrounding towns and for recreational purposes.

River management is an important aspect of water control and conservation in the Massif. Much of the

management in the Cévennes is entrusted to the National Park which is primarily responsible for maintaining

the landscape. Elsewhere Regional River Authorities have implemented various river management

schemes. Good management can only be achieved by gaining a full understanding of the physical

processes acting within river channels - the processes at work today, the erosional history, and the physical

controls of the environment (See Figure 2).

55

Although total yearly precipitation is high in the region, it is as always distribution that is the problem. During

the long, dry summer, water supply may be barely sufficient to meet demand. With an ever-increasing

number of tourists in the region, the problem is becoming more acute. The Departement of Lozère has

become sufficiently concerned to fund research by the University of Alès into the hydrology of the region. It is

hoped that a more efficient way of managing the available water will be found.

Specific Information The Souteyran Valley lies along the southern slopes of Mont Lozère. It contains two rivers, the Souteyran

and Rieumalet, which is a tributary of the former. Both these flow into The Tarn at Le Pont de Montvert. The

rivers are characteristic of upland streams which drain a granite and peat area. The soils are generally

acidic and very thin on the slopes, but are deeper in the valley bottoms where periodic flooding has provided

some input of alluvium. Both rivers are important to the valley communities: The Eagle's Nest relies upon

them for its water supply as do Finiels and Prat Souteyran. In the latter two villages the water from these

rivers has been carefully diverted along small drainage ditches or 'beals' which sometimes appear to be

flowing uphill! Some farmers feed the water into ponds where trout are bred for sale in local markets and to

the restaurant in Le Pont de Montvert. Both rivers flow continuously and much of this flow can be attributed

to a slow release from stores held high up on Mont Lozère. These are peat bogs that play an important role

in the basin hydrological cycle.

Discharge, precipitation and temperature data have been collected daily, from a site close to the Eagles

Nest, since December 1997. This data is available at the Centre or from our Web pages.

River Souteyran Storm Hydrographs In early October 2001, there was a short violent storm around the Eagles Nest. The following data was

collected and may be used to produce a storm hydrograph. The rainfall information was collected by the

centre’s automatic station and the river was measured at centre’s water intake.

Time Rainfall (mm) River Height (m) Discharge (m3/s)

09-00 (03-10-01) 0 0.34 0.041

19-00 (03-10-01) 0 0.34 0.041

20-00 (03-10-01) 0.5 0.38 0.051

21-00 (03-10-01) 6.5 0.39 0.058

22-00 (03-10-01) 1.5 0.43 0.206

23-00 (03-10-01) 0 0.41 0.131

24-00 (03-10-01) 0 0.40 0.068

09-00 (04-10-01) 1 (over 24 hrs) 0.38 0.053

09-00 (05-10-01) 0 0.38 0.051

09-00 (06-10-01) 0 0.35 0.045

66

Later in the month a more prolonged rainfall event occurred, although of similar intensity at times and the

following results were recorded. This provides a useful contrast to the previous shorter event. Photographs

of the River Tarn in Pont de Montvert were taken during this event and are quite dramatic.

Time Rainfall (mm) River Height (m) Discharge (m3/s)

17-10-01 1 0.35 0.045

18-10-01 30 0.37 0.048

19-10-01 19 0.37 0.049

20-10-01 79 0.52 0.687

21-10-01 3 0.55 0.886

22-10-01 0 0.55 0.759

23-10-01 0 0.55 0.734

24-10-01 0 0.54 0.531

25-10-01 0 0.53 0.466

26-10-01 0 0.52 0.437

27-10-01 0 0.51 0.428

28-10-01 0 0.51 0.428

29-10-01 0 0.50 0.361

30-10-01 0 0.48 0.307

01-11-01 1 0.44 0.176

FIGURE 1: The Drainage Basin System

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77

FIGURE 2: Schematic Diagram of the Relative Rates of Downstream Change in Channel Form

Discharge

Sediment Load

Bed Material Size

Average Size

Valley Slope angle

Width

Depth

Channel Slope gradient

Velocity

Hydraulic radius

88

Aims

• To investigate downstream changes within the river channel and to account for the changes which

take place.

• To Investigate if the River Souteyran is a ‘model’ river

• To investigate the potential for flooding in the Souteyran valley and identify flood risk in le Pont de

Montvert.

Hypotheses

• The cross-sectional area increases downstream.

• Bed-load size decreases downstream.

• Bed material will become more rounded downstream.

• Channel efficiency will increase downstream.

• The channel is more efficient at bank-full levels.

• Mean velocity and discharge increase downstream.

• Channel gradient will decrease downstream.

• The Souteyran valley has a low flood risk, but contributes to a high potential flood risk in the river

Tarn, further down the valley, due to a range of factors (vegetation, geology, relief, etc.)

99

Data Collection Sites

Most groups measure between 5 and 10 sites at a variety of locations over a 10km stretch. Please liase with

your group leader over the number and location of the sites that you wish to study. If a large number of sites

are to be visited then considerable planning is necessary. This may involve the splitting of groups to visit

different sites or the allocation of tasks.

Under high flow conditions it may be impossible to sample at some of the more downstream sites.

Equipment Ranging Poles

Tape Measure

Chain

Metre Rules

Callipers

Flow Metres

Stopwatches

Clinometers

pH meter

Conductivity meter

Power’s scale of roundness

1100

Method and Organisation of Study

Task One – Cross Sectional Area and Bedload (Hypotheses 1, 2 and 3)

Channel form is more a measurement of bank-full discharge than any other factor. Discharges lower than

bank-full are likely to have a smaller proportion of excess energy to mould the channel, and although flood

discharges may cause damage and channel change, their effects will be neutralised by the next bank-full

state (once every 1-3 years).

i) Most natural channels are irregular. Where is the 'bank-full' cross section to be measured from?

ii) Climatic conditions have changed dramatically over the last 10,000 years. Is the present river

responsible for the channel erosion?

Method 1. Present flow Cross-section

Measure water surface width and divide into 10 equal intervals – i.e. divide the width by 10. This will mean

that you take 11 depth readings. Your first measurement should be taken directly against one bank and your

last measurement should be taken against the other bank.

At each of the 11 sites measure stream.

Calculate the mean depth.

Cross-sectional area is calculated by multiplying the width by the mean depth.

2. Bank-full Cross-section

Measure the width of the channel.

Measure the distance from the tape to the water surface. This value is added onto the present flow depth

reading (normally once the mean has been calculated). The tape must be held taut and horizontally at bank-

full level.

Cross-sectional area is calculated by multiplying the width by the mean depth.

3. Bedload

At 11 equally spaced points across the stream (ideally the same points that you took your depth readings

from) measure the ‘b axis’ of the FIRST PEBBLE that your finger touches. The ‘b axis’ or width is used as

this is considered to be the most representative axis of most clasts in relation to their size.

Calculate the average size of sediment for the station.

The shape (roundness) of the clast is compared to a Power’s roundness scale.

Task Two – Channel Efficiency (Hypotheses 4 and 5)

Hydraulic Radius

The efficiency of a channel is controlled amount of contact between the bed and banks and the flowing

water. High degrees of contact give high levels of friction and thus make an inefficient channel. The most

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commonly used method for expressing channel efficiency is through the hydraulic radius. This is the ratio of

cross-sectional area (CSA) to wetted perimeter (wp).

Hydraulic radius = CSA/wp

Hydraulic radius is not expressed in any unit, but the higher the figure then the more efficient the channel.

Method In the same location as the cross-section, run the chain along the bank and bed of the stream following all

the contours of the channel. This gives the wetted perimeter at present flow levels. Measure the length

using the tape measure. Note that the wetted perimeter is always greater than the width!

To find the bank-full simply measure the two sections of bank from the surface to the bank-full level and add

this onto the previous reading. The hydraulic radius can now be calculated.

Task Three – Gradient and Average Velocity (Hypotheses 6 and 7)

Method 1. Gradient

Place the ranging poles at either end of a measured 10m stretch of stream.

Using the clinometer, measure and record the gradient of the stream.

2. Using a Flow Metre/Impellor assembly

Measure the width of the stream and divide into 4 equal intervals (this will provide 3 measuring points – ¼,

½, & ¾ across the channel).

At each of these 3 points measure the velocity –set the impellor at ½ of the water depth and ensure that it is

pointing upstream. Make sure that you stand downstream of the impellor when taking readings!

Record the time taken for the impeller to move from start position to finish position.

Calculate the velocity using the formula or chart.

Calculate the mean velocity for the station.

(For hydroprop flow meter chart, see appendix 2.)

1122

Analysis

Cross Sectional Area (Hypothesis 1)

Using the Centre’s Software:

Use the computer program to plot the cross-sections of the river sites. The program will automatically

calculate wetted perimeter, wetted area, hydraulic radius, mean velocity and discharge (cumecs) once all the

relevant data has been inputted. Ask your group leader if you require assistance.

By Hand:

Draw a cross-section of the stream at each survey point. A cross-section is drawn using the width and depth

measurements. Draw a straight line in proportion to the width of the stream channel. Work out a vertical

scale for the depth measurements, this should include the bank-full depth. Calculate the difference in depth

between bank-full and current stream level. At this calculated distance below the bank-full level, draw a

straight line to represent the water surface. This line should be in proportion to the water surface width.

Below the line representing the water surface, mark the 10 depth measurements across the stream. Join up

the points representing the depth of the stream. Mark on the extent of the floodplain on each side of the

channel. Try to use the same scale for all survey points as this will make it easier to compare the differences

downstream.

Ensure the cross-section is fully labelled. Describe any changes in cross-sectional shape and area

downstream. Is there any pattern? Try to give reasons for any trends shown. Does on or more of the sites

not fit the pattern? Use your site descriptions to explain why this might be so.

Bedload Size and Shape (Hypothesis 2 and 3)

Tabulate the results that you obtained for each site. Calculate a mean bedload size for each site.

Refer to your site cross-sections and try to explain the changes in bedload across the stream channel.

Calculate the standard deviation and interquartile range of bedload sizes at each site. Remember this is a

mountain stream prone to flooding. Why might the standard deviation and interquartile range be quite large?

Draw a scatter graph to show changes in bedload downstream. Do you notice a trend? Why?

Channel Efficiency (Hypothesis 4 and 5)

Calculate the hydraulic radius for each site at both present flow and bank-full levels.

How do these change downstream and relate to each other?

How does hydraulic radius relate to other factors measured, especially discharge and velocity?

Mean Velocity and Discharge (Hypothesis 6)

Tabulate your velocity readings and calculate a mean velocity for each site. Describe any patterns in

changes in velocity across the stream channel. Can you account for these patterns? Draw a scatter graph

1133

to show how average velocity varies downstream? Does this show the result that you expected? If not, why

might this be so?

The discharge is the cross-sectional area (m2) multiplied by the average velocity (m/s) and is measured in

cubic metres per second (cumecs). If you have used the Centre’s software, you can tabulate you discharge

directly from your printouts. If not, first calculate the cross-sectional area as described above.

A third method of obtaining discharge measurements for each site is to use Manning’s ‘n’. This can be

calculated using the following formula:

Q=A x

Where Q = Discharge

A = Cross Sectional Area

R = Hydraulic Radius (Area x Wetted Perimeter)

S = Channel Gradient (This must be a tangent, so convert from degree)

n = Manning’s ‘n’. (This is a constant – you will need to select the appropriate constant from

the table below.)

Channel Type Manning’s n

Earth canal, straight

Artificial channel – shuttered concrete

Winding natural river

Natural channel <30m wide, sluggish weedy pools

Mountain rivers, cobbles and boulders

Major rivers >30m wide, clean regular

0.020

0.014

0.035

0.070

0.050

0.025

This method is particularly useful for calculating discharge at bank-full levels since it is not usually possible

to measure velocity under these conditions. By removing the area from the formula it is possible to estimate

a bank-full velocity.

Plot a scatter graph to show how discharge varies downstream. Does it show the pattern you expected? If

not, why might this be so?

Discharge is very closely linked with hydraulic radius. This is the cross-sectional area (m2) divided by the

wetted perimeter (m). The hydraulic radius for each site is given on your computer print out, or can be

calculated by hand. It is an efficiency ratio. The higher the number, the greater the efficiency of the stream

channel. What might the relationship be between discharge and hydraulic radius? You could test for a

relationship by using Spearman’s Rank or Pearson’s Product.

Channel Gradient (Hypotheses 7)

Compare the gradient readings at each of the sites. How do these change downstream?

Most theories relating to the long profile of a stream suggest that gradient should decrease. Why may this

not have happened on the Souteyran?

Is there any relationship between gradient and velocity?

R 0.67S 0.5 n

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Points For Discussion

Comment on trends and anomalies of graphs and calculations. Particular points to consider might be:

Problems encountered by the group in carrying out the planned investigations.

Limitations of the study – length of river, number of samples, methods of sampling etc.

Ways of improving the accuracy of the study. Which methods are the liable to contain the most errors and

can they be improved upon?

What else may affect the results, for example how do humans impact on the river?

How would different weather conditions change the results?

What changes have taken place in pH and dissolved materials (if measured)? How do these relate to other

factors?

Is the Souteyran a typical river? Can it be related to river models?

1155

Appendix 1: Site Of Study Stations

Site

No.

Distance

Downstream

(km)

Altitude

(m)

1 0 1440

2 0.8 1340

3 1.05 1310

4 1.95 1220

5 2.2 1200

6 3.75 1060

7 3.8 1050

8 4.45 1020

9 5.75 960

10 6.95 880

Scale 0 1000m

NN KKeeyy:: -- SSttuuddyy

SSiittee -- RRiivveerr

1166

Downstream Rivers Recording Sheet

Station Station Station

Present Flow Bank full Present flow Bank full Present Flow Bank full

Width (w)

Wetted

Perimeter(w)

Depth (m)

Mean:

Measure from

tape to water

surface

……….

Add to present

flow mean

depth

Measure from

tape to water

surface

……….

Add to present

flow mean

depth

Measure from

tape to water

surface

……….

Add to present

flow mean

depth

Size Shape Size Shape Size Shape

Sediment:

Mean Size &

Shape

Time Taken

Mean Time

Velocity(m/s)

Gradient

pH

Conductivity

1177

RIVER INVESTIGATION RESULTS SHEET

It is recommended that this sheet be filled in with pencil so that any errors can be easily changed.

Station Station Station

Present flow Bank full Present flow Bank full Present flow Bank full

W (w)

m

m

m

m

m

m

Depth (d)

m

m

m

m

m

m

Area (A)

(w x d)

m2

m2

m2

m2

m2

m2

Wetted

Perimeter (P)

m

m

m

m

m

Hydraulic

Radius(A/P)

Present flow only Present flow only Present flow only

Velocity (v)

m/s

m/s

m/s

Discharge (Q)

m3/s

m3/s

m3/s

Conductivity

ppm

ppm

ppm

pH

Gradient (S)

Sediment

Shape

Sediment Size

cm

cm

cm

1188

Possible Project Titles

The following are some possible ideas for projects which students can undertake for coursework using data

collected in this unit.

• The Souteyran River exhibits the classical model of development forwarded by W.M. Davis.

• How do channel variables change downstream?

• To examine the relationships between width and depth, and velocity and discharge along a river

channel.

• Do streams of different orders exhibit different characteristics?

• The Souteyran River becomes more efficient downstream.

• Velocity is related more to channel efficiency than to gradient.

• Sediment size and shape are related to velocity.

• Sediment size and shape will change downstream.

• Channels with small, rounded bed-load are more efficient than those characterised by large, coarse

poorly sorted materials.

• Does velocity change with water depth?

• Abstraction of water has an impact on channel variables within the River Souteyran.

• A comparison of a river channel at bank-full and normal flow conditions.

• Dissolved load and pH are related to geology and land-use.

• Stream channel size and discharge is related to the size of basin area drained.

• Rejuvenation along the Souteyran has directly affected channel variables.

The following titles require more data to be collected on the Souteyran or elsewhere.

• Do streams of the same order exhibit similar characteristics?

• How does discharge relate to rainfall in the Souteyran basin? (Secondary data available in this unit

and at The Eagles Nest).

• Comparison of an upland stream with a lowland stream.

• Comparison of a stream on granite with a different rock type.

• The River Souteyran can be considered to be clean and unpolluted along its course.

1199

Investigating Flood potential in the souteyran Valley.

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11.. CCaattcchhmmeenntt MMaappppiinngg

FFrroomm RRoocc DDuu CCoouuiilllloouu llooookk oouutt oovveerr tthhee SSoouutteeyyrraann vvaalllleeyy aanndd rreeccoorrdd oonn tthhee bbllaannkk bbaassee mmaappss ((AAppppeennddiixx 22 &&

33)) wwhhaatt tthhee ¼¼kkmm22 ssqquuaarreess aarree ddoommiinnaatteedd bbyy,, iinn tteerrmmss ooff::

LLaanndd UUssee::

((11)) DDeecciidduuoouuss wwooooddllaanndd ((DDaarrkk ggrreeeenn))

((22)) CCoonniiffeerroouuss wwooooddllaanndd ((LLiigghhtt ggrreeeenn))

((33)) PPaassttuurree//MMeeaaddooww ((YYeellllooww))

((44)) BBrroooomm ssccrruubb ((OOrraannggee))

((55)) BBaarree ssooiill ((BBrroowwnn))

((66)) BBaarree rroocckk//SSccrreeee ((GGrreeyy))

((77)) PPaavveedd//UUrrbbaann ((BBllaacckk))

aanndd RReelliieeff::

((11)) FFllaatt

((22)) GGeennttllee

((33)) IInntteerrmmeeddiiaattee

((44)) SStteeeepp

((55)) VVeerryy sstteeeepp

((UUssee oonnee mmaapp ffoorr llaanndd uussee aanndd aa sseeccoonndd mmaapp ffoorr rreelliieeff.. TThhee ccoolloouurr ddeessiiggnnaattiioonnss aarree ffoorr tthhee ffoollllooww uupp wwhheenn

pprroodduucciinngg nneeaatt llaanndd uussee mmaappss))

22.. SSiittee eevvaalluuaattiioonn aatt vvaarriioouuss llaanndd uussee ssiitteess::

PPlleeaassee nnoottee tthhaatt tthheerree mmaayy nnoott bbee eennoouugghh ttiimmee ttoo ssttuuddyy aallll llaanndd uusseess iinn ddeettaaiill,, iitt iiss bbeesstt ttoo ccoonncceennttrraattee oonn 33

iinn ppaarrttiiccuullaarr.. OOnn aarrrriivvaall aatt tthhee cceennttrree ddiissccuussss wwiitthh tthhee ccoouurrssee lleeaaddeerr wwhhaatt tthheeyy wwoouulldd rreeccoommmmeenndd.. FFoorr eeaacchh

llaanndd uussee ttyyppee mmaakkee ssuurree yyoouu hhaavvee ssiixx ppiieecceess ooff ddaattaa ((eennoouugghh ffoorr aa MMaannnn WWhhiittnneeyy UU ssiiggnniiffiiccaannccee tteesstt)),,

ddeeppeennddiinngg oonn hhooww mmaannyy ssttuuddeenntt ggrroouuppss tthheerree aarree ssoommee rreeppeeaattss mmaayy nneeeedd ttoo bbee ddoonnee.. AAtt eeaacchh ssiittee ccoonndduucctt

tthhee ffoolllloowwiinngg.. SSeeee rreeccoorrddiinngg sshheeeett ((AAppppeennddiixx 44))::

IInnffiillttrraattiioonn rraattee

CCaarreeffuullllyy wwiitthh tthhee aaiidd ooff tthhee mmaalllleett,, hhaammmmeerr tthhee iinnffiillttrraattiioonn ccaann iinnttoo tthhee ggrroouunndd bbyy aapppprrooxxiimmaatteellyy 33--55ccmm.. WWiitthh

hheeaalltthh && ssaaffeettyy iinn mmiinndd,, iitt iiss bbeetttteerr ffoorr aa mmeemmbbeerr ooff ssttaaffff oorr tthhee ccoouurrssee lleeaaddeerr ttoo ppeerrffoorrmm tthhiiss ooppeerraattiioonn.. OOnnccee

2211

tthhee iinnffiillttrraattiioonn ccaann iiss ffiirrmmllyy iinn tthhee ggrroouunndd,, ppoouurr wwaatteerr iinnttoo tthhee ccaann ttoo aa lleevveell ooff 1100ccmm.. WWiitthh tthhee aaiidd ooff aa mmeettrree

rruulleerr ppllaacceedd iinnssiiddee tthhee ccaann,, rreeccoorrdd tthhee lleevveell ooff tthhee ssuurrffaaccee ooff tthhee wwaatteerr lleevveell aatt 11 mmiinnuuttee iinntteerrvvaallss oovveerr aa ttoottaall

ppeerriioodd ooff 55 mmiinnuutteess ((NNoottee tthhaatt iiff aallll wwaatteerr iinnffiillttrraatteedd bbeeffoorree 55 mmiinnuutteess,, rreeccoorrdd tthhee eexxaacctt ttiimmee ttaakkeenn))..

AAnnggllee ooff ssllooppee..

UUssiinngg aa cclliinnoommeetteerr aanndd rraannggiinngg ppoolleess,, aasssseessss tthhee aannggllee ooff ssllooppee oovveerr aa ssttaannddaarrddiisseedd ddiissttaannccee,, ssuucchh aass 1100mm

mmeeaassuurreedd wwiitthh aa ttaappee mmeeaassuurree..

SSooiill ccoommppaaccttiioonn

UUssee aa sskkeewweerr ttoo ppuusshh ddoowwnn iinnttoo tthhee ggrroouunndd.. RReemmoovvee tthhee ssppiikkee ffrroomm tthhee ggrroouunndd aanndd mmeeaassuurree tthhee ddeepptthh ooff

ppeenneettrraattiioonn ((ii..ee.. hhooww mmuucchh ooff tthhee ssppiikkee ssttuucckk iinn tthhee ggrroouunndd)) wwiitthh tthhee aaiidd ooff tthhee mmeetteerr rruulleerr..

SSooiill tteexxttuurree tteesstt

WWiitthh aa ssooiill ssaammppllee,, ffoollllooww tthhee iinnssttrruuccttiioonnss oonn tthhee ssooiill tteexxttuurree kkeeyy ttoo iiddeennttiiffyy iittss tteexxttuurree..

SSooiill MMooiissttuurree

CCoolllleecctt ssooiill ssaammpplleess ffrroomm tthhee ffiieelldd aanndd ppllaaccee iinn aa sseeaalleedd ccoonnttaaiinneerr.. WWhheenn bbaacckk iinn tthhee llaabb,, wwiitthh tthhee aaiidd ooff

ssccaalleess tthhaatt ccaann mmeeaassuurree ttoo wwiitthhiinn 00..0011gg.. MMeeaassuurree aanndd rreeccoorrdd tthhee mmaassss ooff aann eemmppttyy ccrruucciibbllee.. PPllaaccee aa

ssaammppllee ooff tthhee ssooiill iinn tthhee eemmppttyy ccrruucciibbllee,, mmaakkiinngg ssuurree nnoott ttoo oovveerr ffiillll tthhee ccrruucciibbllee ssoo tthheerree iiss ddaannggeerr ooff ssppiillllaaggee

tthhrroouugghhoouutt tthhee eexxppeerriimmeenntt,, oorr ttoo pprreessss tthhee ssooiill ddoowwnn aanndd ccoommppaacctt iitt wwhhiicchh ccaann iimmppeeddee tthhee eessccaappee ooff

mmooiissttuurree bbyy eevvaappoorraattiioonn tthhrroouugghh tthhee ssooiill ppoorreess.. WWeeiigghh tthhee ccrruucciibbllee wwiitthh tthhee ssooiill ssaammppllee aanndd rreeccoorrdd tthhee

rreessuulltt,, tthheenn ppllaaccee iinn aann oovveenn oorr mmiiccrroowwaavvee ttoo ddrryy tthhee ssooiill ((IIff uussiinngg aann oovveenn ddoo nnoott hhaavvee tthhee tthheerrmmoossttaatt sseett ttoo

hhiigghh ssiinnccee tthheerree iiss aa ddaannggeerr ooff bbuurrnniinngg ooffff tthhee oorrggaanniicc mmaatteerriiaall wwhhiicchh wwoouulldd aaffffeecctt tthhee rreessuulltt.. HHaavvee iitt sseett ttoo

112200°°CC wwhhiicchh iiss ssuuffffiicciieenntt.. IIff uussiinngg aa mmiiccrroowwaavvee,, mmaakkee ssuurree yyoouu aallssoo ppuutt aa sseeppaarraattee vveesssseell ooff wwaatteerr iinn tthhee

mmiiccrroowwaavvee aass wweellll,, bbeeccaauussee iiff tthheerree iiss nnoo mmooiissttuurree iinn tthhee oorriiggiinnaall ssooiill ssaammppllee,, tthhee mmiiccrroowwaavvee ccoouulldd bbee

ddaammaaggeedd ssiinnccee iitt wwoorrkkss bbyy hheeaattiinngg wwaatteerr mmoolleeccuulleess)).. AAfftteerr ttaakkiinngg tthhee ssaammppllee oouutt ooff tthhee oovveenn//mmiiccrroowwaavvee,,

wweeiigghh tthhee ssaammppllee iinn tthhee ccrruucciibbllee tthheenn ppllaaccee bbaacckk iinn tthhee oovveenn//mmiiccrroowwaavvee.. RReeppeeaatt tthhiiss pprroocceessss ttiillll yyoouu rreeaacchh aa

ccoonnssttaanntt mmaassss ttoo bbee ssuurree tthhaatt aallll mmooiissttuurree hhaass eevvaappoorraatteedd..

33.. SSeettttlleemmeenntt

IInn PPoonntt ddee MMoonnttvveerrtt,, SSttuuddeennttss wwiillll ccaarrrryy oouutt aa ccoorrrriiddoorr ssuurrvveeyy aalloonngg tthhee TTaarrnn wwiitthh tthhee aaiidd ooff tthhee bbaassee mmaapp

rreeccoorrddiinngg tthheeiirr oobbsseerrvvaattiioonnss wwiitthh rreessppeecctt ttoo fflloooodd rriisskk aasssseessssmmeenntt aatt tthhee sseelleecctteedd ssiitteess ((AAppppeennddiixx 55 oorr 66))..

2222

AAnnaallyyssiiss

11.. CCaattcchhmmeenntt MMaappppiinngg

PPrroocceessss tthhee ddaattaa bbyy pprroodduucciinngg aa nneeaatt llaanndd uussee mmaapp ((wwiitthh tthhee ccoolloouurr kkeeyy mmeennttiioonneedd iinn tthhee mmeetthhooddoollooggyy)) iinn

tthhee ccllaassss rroooomm,, ssttuuddeennttss wwiillll bbee aabbllee ttoo aasssseessss wwhhaatt tthhee ccaattcchhmmeenntt aarreeaa iiss ddoommiinnaatteedd bbyy oorr iiff tthheerree aarree

ddiissttiinnccttiivvee sseeccttoorrss.. IItt iiss ppoossssiibbllee ttoo wwoorrkk oouutt aa ppeerrcceennttaaggee bbrreeaakkddoowwnn ooff tthhee ddiiffffeerreenntt ccaatteeggoorriieess.. AAllssoo

pprroodduuccee aa nneeaatt mmaapp bbaasseedd oonn tthhee rreelliieeff ddaattaa,, uussee ddiiffffeerreenntt iinntteennssiittiieess ooff oonnee ccoolloouurr ((ssuucchh aass ppuurrppllee)) ttoo

rreepprreesseenntt tthhee ddiiffffeerreenntt ggrraaddeess ooff rreelliieeff wwiitthh tthhee ddaarrkkeesstt bbeeiinngg tthhee sstteeeeppeesstt..

FFlloooodd RRiisskk SSccoorree

FFoorr eeaacchh ooff tthhee ssqquuaarreess ccaallccuullaattee tthhee fflloooodd rriisskk ssccoorree,, wwhhiicchh iiss tthhee LLaanndd uussee ssccoorree ((11--77)) mmuullttiipplliieedd bbyy tthhee

RReelliieeff ssccoorree ((11--55)).. TThhee fflloooodd rriisskk ssccoorree wwiillll vvaarryy ffrroomm 11 ((ffllaatt ddeecciidduuoouuss wwooooddllaanndd;; llooww rriisskk)) ttoo 3355 ((vveerryy sstteeeepp

ppaavveedd//uurrbbaann ssuurrffaacceess;; hhiigghh rriisskk)).. PPrroodduuccee aa nneeww mmaapp wwiitthh tthheessee ssccoorreess ttoo hhiigghhlliigghhtt hhiigghheerr fflloooodd rriisskk aarreeaass..

PPoossssiibbllee eexxtteennssiioonn;; CCaallccuullaattee aann oovveerraallll aavveerraaggee ooff aallll tthhee fflloooodd rriisskk ssccoorreess ttoo ggiivvee aa CCaattcchhmmeenntt fflloooodd rriisskk

ssccoorree.. TThhiiss ccoouulldd bbee uusseedd aass aa mmeeaassuurree ooff ccoommppaarriissoonnss wwiitthh ootthheerr ccaattcchhmmeennttss..

22.. LLaanndd uussee eevvaalluuaattiioonnss

FFoorr eeaacchh ooff tthhee llaanndd uusseess ccaallccuullaattee tthhee::

IInnffiillttrraattiioonn RRaattee

DDiivviiddee tthhee ttoottaall ddrroopp ooff wwaatteerr iinn tthhee iinnffiillttrraattiioonn ccaann ((ccoonnvveerrtt ttoo mmmm)) bbyy tthhee ttiimmee ttaakkeenn ((iinn mmiinnuutteess)).. TThhiiss wwiillll

ggiivvee yyoouu aa rreessuulltt ooff iinnffiillttrraattiioonn iinn mmmm//mmiinnuuttee.. MMuullttiippllyy tthhee rreessuulltt bbyy 6600 ssoo iitt iiss eexxpprreesssseedd iinn mmmm//hhrr.. TThhiiss iiss

tthheenn ccoommppaarraabbllee ttoo rraaiinn ffaallll rraatteess..

SSooiill mmooiissttuurree

UUssee tthhee ffoolllloowwiinngg eeqquuaattiioonn ttoo wwoorrkk oouutt %% ssooiill mmooiissttuurree

((MMaassss ooff oorriiggiinnaall ssooiill ssaammppllee iinn ccrruucciibbllee)) –– ((MMaassss ooff ddrriieedd ssooiill iinn ccrruucciibbllee))

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ xx 110000

((MMaassss ooff oorriiggiinnaall ssooiill ssaammppllee iinn CCrruucciibbllee)) –– ((MMaassss ooff ccrruucciibbllee))

ii..ee.. ((MMaassss lloosstt dduuee ttoo eevvaappoorraattiioonn))

-------------------------------------------------------------------------------- xx 110000 == %% SSooiill MMooiissttuurree

((MMaassss ooff oorriiggiinnaall ssooiill ssaammppllee))

PPoossssiibbllee ttaasskkss;;

MMaannnn WWhhiittnneeyy UU tteesstt ttoo sseeee iiff tthheerree iiss aa ssiiggnniiffiiccaanntt ddiiffffeerreennccee iinn iinnffiillttrraattiioonn bbeettwweeeenn llaanndd uusseess ((HHyyppootthheessiiss 11))..

SSppeeaarrmmaannss RRaannkk CCoorrrreellaattiioonn CCooeeffffiicciieenntt bbeettwweeeenn ssllooppee aannggllee aanndd iinnffiillttrraattiioonn ((HHyyppootthheessiiss 22))

SSppeeaarrmmaannss RRaannkk CCoorrrreellaattiioonn ccooeeffffiicciieenntt oonn ssooiill mmooiissttuurree vveerrsseess iinnffiillttrraattiioonn rraattee ((HHyyppootthheessiiss 33))..

2233

CCoonnssiiddeerraattiioonnss oonn ssttaattss tteessttss;;

NNuummbbeerr 11 ddooeess nnoott ttaakkee iinnttoo aaccccoouunntt tthhee iinnfflluueennccee ooff tthhee ssllooppee ooff tthhee llaanndd,, ssooiill tteexxttuurree oorr tthhee aanntteecceeddeenntt

mmooiissttuurree..

NNuummbbeerr 22 ddooeess nnoott ttaakkee iinnttoo aaccccoouunntt tthhee llaanndd uussee,, ssooiill tteexxttuurree oorr aanntteecceeddeenntt mmooiissttuurree..

NNuummbbeerr 33 ddooeess nnoott ttaakkee iinnttoo aaccccoouunntt tthhee llaanndd uussee,, ssooiill tteexxttuurree oorr aannggllee ooff ssllooppee

33.. SSeettttlleemmeenntt EEvvaalluuaattiioonn

LLooookkiinngg aatt tthhee ccoorrrriiddoorr mmaappppiinngg ffrroomm PPoonntt ddee MMoonnvveerrtt wwiitthh tthhee ssttuuddeennttss’’ oobbsseerrvvaattiioonnss.. DDiissccuussss hhooww aatt rriisskk

tthhee sseettttlleemmeenntt iiss ffrroomm ffllooooddiinngg aass aa rreessuulltt ffrroomm eexxttrreemmee wweeaatthheerr aanndd wwhhaatt iiss pprreesseenntt ttoo lliimmiitt tthhee ddaammaaggee ooff

ffllooooddiinngg ((SSuucchh aass cchhaannnneell mmooddiiffiiccaattiioonnss,, hhiigghh bbrriiddggee aanndd wwaallll bbyy rrooaadd,, bboottttoomm fflloooorr uusseedd aass cceelllleerr)).. PPrroodduuccee

aa nneeaatt fflloooodd aasssseessssmmeenntt mmaapp uussiinngg IIGGNN PPoonntt ddee MMoonnttvveerrtt bbaassee mmaapp ((AAppppeennddiixx 77)) bbaasseedd ffrroomm oobbsseerrvvaattiioonnss

aanndd ccoommppaarree ttoo aaccttuuaall fflloooodd aasssseessssmmeenntt mmaapp ((AAppppeennddiixx 88)).. WWoorrkk oouutt wwhhaatt tthhee iimmppaaccttss ooff ppootteennttiiaall ffllooooddiinngg

wwoouulldd bbee.. DDiissccuussss tthhee aaddvvaannttaaggeess aanndd ddiissaaddvvaannttaaggeess ooff ppoossssiibbllee fflloooodd mmaannaaggeemmeenntt tteecchhnniiqquueess,, wwiitthh

rreeffeerreennccee ttoo ccoosstt bbeenneeffiitt aannaallyysseess..

PPoossssiibbllee mmeetthhooddss ooff fflloooodd ddeeffeennccee//fflloooodd rriisskk rreedduuccttiioonn..

CChhaannnneell mmooddiiffiiccaattiioonn..

DDaamm..

AAffffoorreessttaattiioonn..

DDiiffffeerreenntt ffaarrmmiinngg tteecchhnniiqquueess,, ccoonnttoouurr pplloouugghhiinngg..

PPooiinnttss FFoorr DDiissccuussssiioonn

BBrriinngg aallll tthhrreeee eelleemmeennttss ttooggeetthheerr iinn aa ccllaassss ddiissccuussssiioonn..

WWhhiicchh ppaarrttss ooff tthhee ccaattcchhmmeenntt ccoonnttrriibbuuttee mmoosstt ttoo fflloooodd rriisskk??

DDooeess pprreecciippiittaattiioonn eexxcceeeedd iinnffiillttrraattiioonn lleeaaddiinngg ttoo ssuurrffaaccee rruunn ooffff wwhhiicchh iinnccrreeaassee fflloooodd rriisskk??

WWhhaatt tteecchhnniiqquueess ffuurrtthheerr mmaannaaggeemmeenntt ppllaannss ccoouulldd bbee uuttiilliisseedd ttoo ffuurrtthheerr lleesssseenn tthheessee ppootteennttiiaall fflloooodd rriisskkss??

AArree tthheessee mmeeaassuurreess ccoosstt eeffffeeccttiivvee??

HHooww ddoo yyoouu tthhiinnkk tthhiiss ccaattcchhmmeenntt ccoommppaarreess ttoo aa llooccaall eexxaammppllee nneeaarr yyoouu??

2244

AAppppeennddiixx 11::

2255

AAppppeennddiixx 22::

2266

AAppppeennddiixx 33::

2277

AAppppeennddiixx 44:: SSiittee eevvaalluuaattiioonn rreeccoorrddiinngg sshheeeett

LLaanndd uussee

AAnnggllee ooff ssllooppee

SSooiill ccoommppaaccttiioonn

SSooiill TTeexxttuurree

SSttaarrtt

11 mmiinn

22 mmiinn

33 mmiinn

44 mmiinn

II nnff ii ll

tt rr aatt ii oo

nn rr aa

tt ee,, hh

ee iigg hh

tt ooff ww

aa ttee rr

55 mmiinn

TTiimmee iiff aallll wwaatteerr

iinnffiillttrraatteedd iinn lleessss tthhaann 55

mmiinn

AAppppeennddiixx 55::

2299

AAppppeennddiixx 66::

3300

AAppppeennddiixx 11.. HHyyddrroopprroopp FFllooww MMeetteerr CChhaarrtt..