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Comparative Simulation of the effects of environmental change on Rhine floods Motivation Munich Re, 2010 Munich Re, 2010 Incre crease ase in n in numb umber er of fl of flood ood ev events ents (le (left) ft) and and rel relate ated dam d damage ages ( s (right right)

Comparative Simulation of the effects of environmental change on Rhine floods Motivation What is What is the impa the impact of en ct of environmen vironmental chan tal changes ges on flood on flooding cond ing conditions ? itions ? ? ? Land use change Land use change ? Climate Climate change change ? River tr River training m aining measures easures ? Anything Anything else else ? Nothing Nothing at all at all

Comparative Simulation of the effects of environmental change on Rhine floods Motivation Th The Rhi e Rhine ne:  3 rd biggest European river  Most important European river Rh Rhine action ine action p pla lan for n for flood defenc fl ood defence e (I (ICPR,1998): CPR,1998):  Reduce damage risks by 25%  Reduce flood stages downstream impounded reaches up to 70cm  Increase flood risk awareness  Improve flood forecasting Qu Quantificati antification on n needed !! eeded !!

Comparative Simulation of the effects of environmental change on Rhine floods Major environmental changes in the Rhine basin during the last century 1) Urbanisati Urbanisation on  doubling of urban areas (housing, industry, traffic doubling of urban areas (housing, industry, traffic etc.) during the last 60 years etc.) during the last 60 years  Reduction of farm land Reduction of farm land  50  199 Examples: Examples: Körsch -Catchment Catchment 1850 990 850  1980 Mann annheim / Ludw udwigshafen 1850 980

Comparative Simulation of the effects of environmental change on Rhine floods Major environmental changes in the Rhine basin during the last century 2) 2) dece decent ntralis ralised ed stor storm m water water m manage anageme ment nt  retention on roofs etc. retention on roofs etc.  Small scale retention Small scale retention in the landscape in the landscape

Comparative Simulation of the effects of environmental change on Rhine floods Major environmental changes in the Rhine basin during the last century 3) 3) Changed m Changed man anag agement prac ement practi tice ce of farm l of farm lan and  conventional tillage vs. conventional tillage vs. ecological oriented ecological oriented tillage tillage  rationalisation of farm rationalisation of farm land land

Comparative Simulation of the effects of environmental change on Rhine floods Major environmental changes in the Rhine basin during the last century 4) 4) river tra river train inin ing and rive g and river r ch channelling annelling 1820 ca. 1800 1870 1990 today  faster flood wave propagation faster flood wave propagation  reduced retention in flood plains reduced retention in flood plains

Comparative Simulation of the effects of environmental change on Rhine floods Major environmental changes in the Rhine basin during the last century 5) 5) Climate c Climate cha hang nge Persistence of weather type „Western - Zonal“, 1900 - 1990. (Bárdossy, 1995) Annual precipitation over the Rhine Area upstream Köln. (Engel, 1995)

Comparative Simulation of the effects of environmental change on Rhine floods Major environmental changes in the Rhine basin during the last century 5) 5) Climate c Climate cha hang nge Months / 50 years with frozen river surface at Köln. (Krahe, 1997) Timing of spring flood peak flood at gauge Maxau 1920 - 2000 (Bürger, 2002)

Comparative Simulation of the effects of environmental change on Rhine floods The modelling concept 1) 1) Sto Storm rm ru runoff g noff gene eneration ration in influenc fluenced ed by lan by land u d use se  process process-or oriente ented d modelling ing in some sub-catch atchme ments ts 2) 2) Regional egionalizat izatio ion of of runoff runoff gene genera ration ion  macro scale hydrol. . modelling ling in all sub-catchmen atchments ts 3) 3) Flood ro lood routin uting g and r nd retentio etention in n in f flood ood plains plains  hy hydr drod odynam ynamic ic ro rout uting ing in in th the e ma main in ri rive ver r sy syst stem em 4) 4) Modellin odelling of g of t the wh e whole hyd ole hydrolo rologi gical al-hydrauli ydraulic sy c syst stem m  meteorologica ological l perturb rbation tions s / climate e scenari rios

Comparative Simulation of the effects of environmental change on Rhine floods The modelling approach: nested and scale-specific models

Comparative Simulation of the effects of environmental change on Rhine floods I process-oriented modelling The Lein The Lein Sub Sub-Ca Catchm tchmen ent: Area: 115 km² Area: Location: Location: Kraichgau (SW- Germany); land use: land use: intensive agriculture Rotterdam Arnhem soils: soils: deep loess soils Lenne ( = 455 km²) A E Köln Wiesbaden Mainz Lein ( = 115 km²) A E Körsch Karlsruhe ( = 127 km²) A E Strasbourg Basel

Comparative Simulation of the effects of environmental change on Rhine floods WASIM-ETH (Schulla, 1979) grid based (fully distributed)  process oriented:  interception,  evapotranspiration,  quick runoff (‘Hortonian overland flow’;  saturation overland flow) inter flow  ground water response  extended version (Niehoff, 2002): agricultural areas ( macropore flow; sealing )  urbanized areas ( sealed vs. non-sealed;  decentralized storm water infiltration ) (Niehoff, 2002) water retention in the landscape  Process-oriented hydrological Model: extended WASIM-ETH

Pa Paramet rameter ers for s for t the ex he exte tended nded WA WASIM SIM-ETH ETH-mo mode del l

Comparative Simulation of the effects of environmental change on Rhine floods Results I: The Lein sub-catchment Niehoff et al. 2002 Simul Si ulate ted sto storm m run unoff a ff afte ter ( (a) a ) a con onvec ective ive rai ain e event ent (b) b) an an advec vectiv tive rai e rain e n even vent; pr t; prese esent nt land land use use an and urb d urbani anisat sation s ion scen cenari arios os

Comparative Simulation of the effects of environmental change on Rhine floods Results I: The Lein sub-catchment Convective rainfall events Advective rainfall events Saturation excess Saturation excess infiltration excess Sewage channel Sewage channel infiltration excess excess excess xxx Subsurface Slow ground- Slow groundwater flow storm flow water flow Subsurface storm flow Niehoff et al. 2002 Lein Lein-sub sub-catchment: runoff generation processes for catchment: runoff generation processes for different rainfall event types different rainfall event types

Comparative Simulation of the effects of environmental change on Rhine floods Results I: The Lein sub-catchment Year, month Increase in runoff Simulated baseflow Duration Return compared to present contribution [h] period conditions to volume [%] approx. [a] Maximum Volume [%] [%] 1990, February 3,4 3,7 19 150 2 1993, December 5,9 2,7 17 250 8 1997, February 3,9 2,7 19 150 7 1982, December 1,7 1,5 27 225 3 1983, May 0,6 0,9 39 300 4 1988, March 0,0 0,0 52 650 3 Mean 2,6 1,8 29 290 4,5 Increase in runoff volume and peak due to a 50 % growth of settlement and industrial areas in the Lein catchment. The events are sorted by the urbanisation impact on runoff volume

Comparative Simulation of the effects of environmental change on Rhine floods Results II: The Lenne sub-catchment The Lenn The Lenne sub e sub-catc catchm hmen ent Area: Area: 455 km² Location: Location: Sauerland (W-Germany); Rotterdam Arnhem Land Use: mainly forest and pasture; Land Use few settlement Lenne ( = 455 km²) A soils: soils: shallow, permeable E Köln hydro drolog logical ical mod model: el: extended WASIM-ETH Wiesbaden Mainz Lein ( = 115 km²) A E Körsch Karlsruhe ( = 127 km²) A E Strasbourg Basel

Comparative Simulation of the effects of environmental change on Rhine floods Results II: The Lenne sub-catchment Niehoff et al. 2002 Simulate storm runoff after (a) a convective rain event (b) an advective rain event; present land use and urbanisation scenarios