Morphology and Floods in the Alpine Region

Transcription

1 Morphology and Floods in the Alpine Region Benno Zarn, Hunziker, Zarn & Partner AG, CH-Domat/Ems KHR, From the Source to mouth, a sediment budget of the Rhine River March 2015, Lyon France Content 1. Catchment 2. Hydrology 3. River Training - Morphology 4. Bed load transport 1

2 1. Catchment drainage area: km 2 average altitude: a.s.l. glaciation: < 1.4% 100-year flood: m 3 /s bed load: m 3 /y suspended load: 3 Mio. m 3 /y Bodensee CH DE AT Ill LI Vorderrhein Plessur Hinterrhein Lai da Toma IT 2 Catchment

3 Geology schist 3 Catchment

4 AT Val Parghera CH LI Val Pargehra Alpenrhein IT schist 4 Catchment

5 tributaries moraine, sediment source Plessur narrowing Hinterrhein (Domleschg) about 200 years ago 5 Catchment

6 1927 flood torrent control e.g. Schraubach CH LI AT Rutschung Schuders um 1950, Mio. m3 IT Dammbruch Buchs / Schaan [ m a.s.] [m] river training - morphology Schraubach

7 1999, Hydrology main divide Alpenrhein Süd, hydrology 1834, 1868, 1927, 1954, (2002) Nord, 1910

8 large floods in the past 4 catastrophic floods extrem large floods very large floods large floods hydrology

9 1927- and 1987 floods Rhine gorge ruin aulta (Vorderrhein) 9 hydrology

10 Spullersee Inbetriebnahme 1925 Silvretta 1951 Marmorera 1954 Nalps, Valle di Lei 1959 Zervreila 1958 Lünersee 1959 Spullersee 1965 hydro power storage basin storage volume [10 6 m 3 ] Curnera 1966 Kops 1967 St. Maria 1968 Gigerwald 1976 Panix 1992 Buchs Sargans Mapragg Gigerwald Feldkirch Vaduz Rodund Ragall Latschau Vermunt Spullersee Kops Panix Reichenau Chur Silvrettasee Davosersee Curnera Nalps Santa Maria Zervreila Sufers Valle di Lei Solis Marmorera 10 hydrology

11 average hydrograph bevor/after storage construction discharge [m 3 /s] Domat/Ems E 3229 km Januar Februar März April Mai Juni Juli August Sept. Oktober Nov. Dez after construction storage basin befor construction storage basin [h] decrease snowmelt runoff about m 3 /s increase winter discharge (average 30 up to 60 m 3 /s, daily changes up to 180 m 3 /s) reduction of the sediment transport capacity of about factor hydrology

12 3. River training - morphology - systematically since ca narrowing to increase the bed load transport capacity - example downstream mouth River Tamina Mastrilser Rheinauen Dufourkarte, blau eingefärbt heutiger Flusslauf 12 river training - morphology

13 Bodensee Fussach Vorarlberg St. Gallen St. Margrethen Altstätten Hard Lustenau Diepoldsau Ill Feldkirch Vorarlberg Fürstentum Liechtenstein Buchs Schaan Vaduz Ellhorn Sargans Balzers Fürstentum Liechtenstein Graubünden 30 Bad Ragaz Tamina St. Gallen Graubünden Mastrilser Rheinauen Vorderrhein Plessur Chur Reichenau Hinterrhein 13 river training - morphology

14 Bodensee Fussach Vorarlberg St. Gallen St. Margrethen Altstätten Hard Lustenau Diepoldsau Ill Feldkirch Vorarlberg Fürstentum Liechtenstein Buchs Schaan Vaduz Ellhorn Sargans Balzers Fürstentum Liechtenstein Graubünden 30 Bad Ragaz Tamina St. Gallen Graubünden Mastrilser Rheinauen Vorderrhein Plessur Chur Reichenau Hinterrhein 14 river training - morphology

15 cut at Fussach ( ) Bodensee Fussach Vorarlberg St. Gallen St. Margrethen Altstätten Hard Lustenau Diepoldsau 70 Buchs Ill Feldkirch Vorarlberg Fürstentum Liechtenstein Schaan Vaduz pre stretch at the mouth since 1972 Ellhorn Sargans Balzers Fürstentum Liechtenstein Graubünden 30 Bad Ragaz Tamina St. Gallen Graubünden Mastrilser Rheinauen meander cut at Diepoldsau ( ) Vorderrhein Plessur Chur Reichenau Hinterrhein 15 river training - morphology

16 Vorder-/Hinterrhein Wehr Reichenau Felsberg Waffenplatz Ellhorn Buchs alte Mündung Plessur Ill erosion between 1950 and 1974 [m] / / / / distance [km] 16 river training - morphology

17 gravel mining gravel mining [10 6 m 3 ] km km km Brücke Buchs/Schaan über den Alpenrhein, Einsturz 1972, Werdenberger Jahrbuch 17 river training - morphology

18 Vorder-/Hinterrhein Plessur Ill Lake of Constance gravel mining ca m 3 /year 4. Bed load transport bed load transport model calibration parameter reference - gravel mining Lake of Constance (observed) - variation mean bed level (observed) parameter changeable - grain size (inside observation range) - bed load input [m 3 /year] 80'000 average annual bed load transport '000 60'000 50'000 40'000 30'000 20'000 10' distance [km] 18 bed load transport

19 Felsberg Waffenplatz Waffenplatz Ellhorn Buchs erosion Wehr Reichenau Plessur aggradation Ill Felsberg Ellhorn Buchs erosion Wehr Reichenau Plessur aggradation Ill 2.0 [m] mean bed level change Mastrilser Rheinauen 1.0 observed calculated model 1 calculated model distance [km] [m] mean bed level change Mastrilser Rheinauen observed calculated model 1 calculated model distance [km] 19 bed load transport

20 Waffenplatz Ellhorn Felsberg Buchs erosion Wehr Reichenau aggradation Plessur Ill comparison mean bed level change: - prediction 22 years (regime ) - observation 15 years ( ) 2.0 [m] observed GM5) / predicted -1.5 distance [km] bed load transport

21 mining bevor 1974 not showed verification model parameter as calibration except - discharge (bed load input by tributaries) - gravel mining as observed bed load input by Maschänser Rüfi (debris flow) 60'000 50'000 [m 3 /Jahr] calibration : 43'500 m 3 /year gravel mining at mouth of River 40'000 30'000 verification : 18'700 m 3 /year 20'000 10' bed load transport

22 Waffenplatz Ellhorn Felsberg Buchs erosion Wehr Reichenau aggradation Ill Plessur Verification [m] /96? calculated Run3) observed GM5) predicted -1.5 distance [km] Probable explanation for the differences 1 local effect 2 bed load transport as «waves»? 3 underestimation bed load input Vorderrhein/ Plessur? 4 underestimation bed load input, Ill? / grain size? 22 bed load transport

23 Conclusion - understanding of the past is necessary for prediction - bed load budgets are the first step - second step: models - third step: better understanding of the processes and alterations in the tributaries for adequate assumptions of the bed load input in the main river 23 bed load transport