Consequences of river regulation works: altered fluvial

SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY

September 7-11, 2005 ZARAGOZA

Consequences of river regulation Consequences of river regulation works: works:

altered fluvial processes + altered fluvial processes + increasing flood hazardincreasing flood hazard

Dr. Dr. TTíímeamea Kiss Kiss assistant professor assistant professor

DepartmentDepartment ofof PhysicalPhysical GeographyGeography andand GeoinformaticsGeoinformatics, , UniversityUniversity ofof Szeged, HungarySzeged, Hungary

20020066.. WVU, MorgantownWVU, Morgantown

Map of Hungary



What is the problem?What is the problem?

2001

2001

2006

2006

Problem: Problem: IncreasingIncreasing floodflood levellevel →→ hazardhazard

Yearly highest water levels on the fluviometer at Mindszent

Increase in flood levelsbetween 1901 and 2006



What can be the possible cWhat can be the possible causesauses ofof thetheincreasingincreasing floodflood levelslevels? ?

Climate (storminess)

Land-use (canopy)

Horizontal (migration)

Vertical (narrowing)

Roughness (vegetation)

Aggradation

Buildings, new constructions

Increasing height and frequency

of floods

Changes on the catchment

Changes on the floodplain Changes on the

channel

Artificial vs. natural

1. Natural and economic conditions before regulation works 1. Natural and economic conditions before regulation works (mid(mid--1919thth c.)c.)

2. Engineering works 2. Engineering works (late 19(late 19thth c., early 20c., early 20thth c.)c.)3. Consequences3. Consequences4. Present4. Present--day situationday situation

ContentContent



1. Conditions before regulations1. Conditions before regulationsNatural:

-Huge floodplain

(swamps)

-Long-lasting floods

Social-economic:

-increasing population

-Opened W-Eu market

-Eneneering

-Financial background

+ PEACE!

2. 2. HistoryHistory ofof riverriver managementmanagement

The The „„ggreatreat”” (19(19thth c.) river regulationsc.) river regulationsFrom 1846 until From 1846 until thethe 18901890’’s s Uniform ideas on the whole Uniform ideas on the whole catchmentcatchment



1.1. CutCut--offs offs (T(Tiszaisza:: 102 places)102 places)→→ decreased length (1214decreased length (1214 →→761 km)761 km)→→ increased gradient (3,7increased gradient (3,7→→7cm/km)7cm/km)→→ SemiSemi--natural natural channelchannel developmentdevelopment

22. . Levee constructionLevee construction→→ flood protected area 26,500 kmflood protected area 26,500 km22

→→ length: 2940 kmlength: 2940 km→→ Semi natural Semi natural floodplainfloodplain

developmentdevelopment3. 3. Drainage systemDrainage system (40,000 km)(40,000 km)

2. 2. HistoryHistory ofof riverriver managementmanagementThe The „„ggreatreat”” (19th c.) river regulations(19th c.) river regulations

2. 2. HistoryHistory ofof riverriver managementmanagementRiver management in the 20River management in the 20thth centurycentury

Floodplain:Floodplain:hardly mahardly maiintainedntained

(dense vegetation, aggradation, (dense vegetation, aggradation, ((il)legalil)legal constructions)constructions)

Levees:Levees:continuous heightening continuous heightening

((locallocal, not enough), not enough)Channel:Channel:

bank bank stabilisationstabilisationfollowing following locallocal ideas and designideas and design

1. Revetment1. Revetmentss260 km on the 590 km long section260 km on the 590 km long section

2. 2. GroyneGroyness189 189



3. Consequences3. ConsequencesCCutut--offsoffs

INCISION

Lowering the water table

Land slidesFast, GREAT floods

Fish population

Land-use changesClimate change

Shortened

Extra sediment load

Increased gradient

Pattern change

widening

Floodplain aggradation

Present slope conditions

3. Consequences:3. Consequences:CCutut--offsoffsCChannelhannel

slope changesslope changes



3. Consequences:3. Consequences:CCutut--offsoffsincisionincision

3. Consequences:3. Consequences:CCutut--offsoffsincisionincision

width depth

Max (m) mean (m) max (m) mean (m) shape index

Area (m2)



3. Consequences:3. Consequences:CCutut--offsoffs

pattern changepattern change

3. Consequences3. Consequenceslevee constructionslevee constructions

Lowered

water table

Micro-climate change (dryer,

warmer)

Soil alterations

(salinization, dry-land solis)

Decreased area of wetlands

Need of irrigation

Artificial (active) floodplain Protected (inactive) floodplain

Inland water problems(active subsidence, no accumulation)

narrow

Large sediment

imput Intensive aggradation

Altered land-use, Invasive species

High floods

(5 m water-depth)

GREAT, large floods

High friction



3. Consequences3. Consequenceslevee constructionlevee construction

Intensive accumulationIntensive accumulation





0,0

0,5

1,0

1,5

2,0

2,5

3,0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

szelvények

(m)

hullámtéri akkumuláció mértéke



Amount of aggradation (m)


WetWet--land reductionsland reductions

I. Military survey (late 18th c.)

II. Military survey (late 19th c.)



I. Military survey (late 18th c.)

Topographical map (1980)


WetWet--land reductionsland reductions

3. Consequences3. Consequenceslevee constructionlevee constructionSalinizationSalinization



3. Consequences3. Consequencesrevetment constructionsrevetment constructions

Narrowing due to dense riparian vegetation

Large sediment

imput

No lateral erosion

Smaller cross-section

GREATer, large floods

Slight incision

Active point-bar formation

Smaller flood conductivity

Sharper bends

Slope decrease

Tisza, Szolnok

Same discharge – increasing flood height

Something wrong!!Something wrong!!

DDischargeischarge –– Stage (water level) Stage (water level)

Rising s

tage

Falling stage



In case of freely developing meanders

3. Consequences3. Consequencesrevetment constructionrevetment construction

Revetment construction (1940), upper section straightened (1886)

3. Consequences3. Consequencesrevetment constructionrevetment construction



CrossCross--sectionalsectional changeschanges

at inflexion point

in axis of meander

at revetment

Decrease of cross-s. area 2-3%

Decrease of cross-s. area 4-6 %

Decrease of cross-s. area 6-19 %

Flood conductivity ??

FloodFlood conductivityconductivity chageschages duedue toto alteredaltered crosscross--sectionalsectional parametersparameters



decliningdeclining-- 66--13 %13 %

((worseworse thanthan ininnaturalnatural statestate))

narrowernarrower, , deepdeepchannelchannel

areaarea decreasedecrease

lowlow sinuositysinuositynarrowingnarrowing bendsbends

2020thth c. c. regulationsregulations((sincesince 19301930’’s)s)

revetmentsrevetments

higherhigher+2+2--3 %3 %

widewide, , deeperdeeperchannelchannel

areaarea increaseincrease

lowerlower sinuositysinuositylargelarge bendsbends

1919thth c. c. regulationsregulations(1890(1890-- 1929)1929)

cutcut--offsoffs

normalnormalwidewide channelchannellargelarge areaarea

highhigh sinuositysinuositynarrownarrow bendsbends

NaturalNatural statestate

FloodFloodconductivityconductivity

CrossCross--sectionssectionsPlanimetryPlanimetry

ConclusionsConclusionsRiver management vs. channel development

What to do now? What to do now?

To do nothing = heroic work, spending money during flood (on nothing)



What to do now? What to do now?

Climate (storminess)

Land-use (canopy)

Horizontal (migration)

Vertical (narrowing)

Roughness (vegetation)

Aggradation

Buildings, new constructions

Changes on the catchment

Changes on the floodplain

Changes on the channel

River restoration? New ways of river and watershed management?

Decrease run-off:Stream restoration?

Land-use optimalization?Storage lakes?

Decrease roughness:Floodplain restoration?

Land-use optimalization??

Increase flood conductivity:Channel restoration?Removal of levees?

Land-use optimalization??

Learn from our mistakes!Learn from our mistakes!

-Long river regulation history

-To monitor changes:

long hydrological data set: water level data (since the 1860’s)

precise Q data (since 1960’s)

spatial data: map series (first survey 1790”s)

cross sections (since 1890)

-Easy to start the devil’s circle

(continuous maintenance should be needed)



ThankThank youyou forfor youryour attentionattention!!

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Consequences of river regulation works: altered fluvial