Consequences of river regulation works: altered fluvial ...pages.geo.wvu.edu/~kite/2006 Kiss...
Transcript of Consequences of river regulation works: altered fluvial ...pages.geo.wvu.edu/~kite/2006 Kiss...
-
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
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
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
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
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
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
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
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
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
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
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
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
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)
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
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
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
3. Consequences3. Consequenceslevee constructionlevee construction
Intensive accumulationIntensive accumulation
3. Consequences3. Consequenceslevee constructionlevee construction
Intensive accumulationIntensive accumulation
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
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
3. Consequences3. Consequenceslevee constructionlevee construction
Intensive accumulationIntensive accumulation
Amount of aggradation (m)
3. Consequences3. Consequenceslevee constructionlevee construction
WetWet--land reductionsland reductions
I. Military survey (late 18th c.)
II. Military survey (late 19th c.)
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
I. Military survey (late 18th c.)
Topographical map (1980)
3. Consequences3. Consequenceslevee constructionlevee construction
WetWet--land reductionsland reductions
3. Consequences3. Consequenceslevee constructionlevee constructionSalinizationSalinization
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
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
stage
Falling stage
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
In case of freely developing meanders
3. Consequences3. Consequencesrevetment constructionrevetment construction
Revetment construction (1940), upper section straightened (1886)
3. Consequences3. Consequencesrevetment constructionrevetment construction
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
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
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
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)
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
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)
-
SIXTH INTERNATIONAL CONFERENCE ON GEOMORFOLOGY
September 7-11, 2005 ZARAGOZA
ThankThank youyou forfor youryour attentionattention!!