Das Augusthochwasser 2002 im Osterzgebirge und dessen statistische Bewertung The extreme flood in August 2002 in the eastern part of the Ore Mountains and its statistical assessment Andreas Schumann Ruhr- Universität Bochum Lehrstuhl für Hydrologie, Wasserwirtschaft und Umwelttechnik 2 The extreme flood in August 2002 in the eastern part of the Ore Mountains and its statistical assessment z The hydrological event z Statistical evaluation of the flood event z How realistic is the statistical assessment ? 3 The extraordinary level of the flood 2002 in relationship to flood peaks of the past (since 1771) at an old building in the city of Grimma at the Mulde River in Germany 4 Meteorological reason for the floods in August 2002 - Vb- Circulation Pattern 5 Spatial Distribution of the extreme precipitation from August 10 to August 13, 2002 in the German part of the Ore Mountains PMP and Area in sq.km Duration 24 hours Duration 72 hours measured Region rainfall maxima Station Zinnwald 1 to 25 km2 350 mm 312 mm 500 mm 406 mm in August 2002 Region Zinnwald 1.000 km2 300 mm 450 mm Part of the Elbe 5.000 km2 200 mm 275 mm River Basin Watershed Upper 12.000 km2 160 mm 250 mm Elbe Precipitation between August 11 and 13, 2002 in mm PMP with a duration of 12 hours for watersheds with 500 km2 in size in summer (June to August) 7 Areal precipitation values from August 10 to 13 2002 for watersheds in the Ore Mountains 450 Area Precipitation 400 10.8.- 13.08.2002 350 300 250 200 150 100 50 0 0 100 200 300 400 500 600 700 800 900 1000 Watershed Size km2 Temporal distribution of the precipitation from August 8 11 to 13 for different river basins in Saxonia Pegel Göritzhain/ Chemnitz Pegel Niederschlema/ Zwickauer Mulde Pegel Cotta/ Verein. Weisseritz Pegel Nossen/ Freiberger Mulde 25 20 Pegel Nossen/ Freiberger Mulde 15 Pegel Cotta/ Verein. Weisseritz 10 Pegel Niederschlema/ Zwickauer Mulde 5 0 Pegel Göritzhain/ Chemnitz 11.08.2002,13:00 11.08.2002,16:00 12.08.2002,1:00 11.08.2002,19:00 12.08.2002,4:00 11.08.2002,22:00 12.08.2002,7:00 12.08.2002,10:00 12.08.2002,13:00 12.08.2002,16:00 13.08.2002,1:00 12.08.2002,19:00 13.08.2002,4:00 12.08.2002,22:00 13.08.2002,7:00 13.08.2002,10:00 9 Temporal distribution of runoff from August 11 to 14, 2002 for different river basins in Saxonia Pegel Niederschlema/ Zwickauer Mulde Pegel Göritzhain/ Chemnitz Pegel Nossen/ Freiberger Mulde Pegel Cotta/ Verein. Weisseritz 5 4.5 4 3.5 3 2.5 2 Pegel Cotta/ Verein. Weisseritz 1.5 Pegel Nossen/ Freiberger Mulde 1 0.5 Pegel Göritzhain/ Chemnitz 0 Pegel Niederschlema/ Zwickauer Mulde 11.08.2002,13:00 12.08.2002,1:00 11.08.2002,17:00 12.08.2002,5:00 11.08.2002,21:00 12.08.2002,9:00 12.08.2002,13:00 13.08.2002,1:00 12.08.2002,17:00 13.08.2002,5:00 12.08.2002,21:00 13.08.2002,9:00 13.08.2002,13:00 14.08.2002,1:00 13.08.2002,17:00 14.08.2002,5:00 13.08.2002,21:00 14.08.2002,9:00 14.08.2002,13:00 14.08.2002,17:00 Linear regression between direct runoff (in mm) and 10 area precipitation for the flood in August 2002 400 Qsum = -58.9 + 0.76*Psum 300 200 Qsum 100 R- (adjusted for d.f.) = 0 87,8 percent 130 180 230 280 330 380 430 Psum Polynomial regression between direct runoff (in mm) 11 and area precipitation for the flood in August 2002 400 Qsum = 82.68-0.436*Psum + 0.002344*Psum^2 300 200 Qsum 100 R-(adjusted for d.f.) = 0 89,4 percent 130 180 230 280 330 380 430 Psum 12 100 70 40 10 -20 Qsum = -24.4309 + 0.741528*Psum - 0.0472646*SBE -50 340 440 540 640 740 840p SBE 190 140 Impact of the soil storage 90 capacity SBE in mm and the total sum of 40 precipitation PSUM on the -10 direct runoff -60 -110 130 180 230 280 330 380 430 Psum 13 Runoff coefficients in relationship to sum of precipitation Runoff Coefficient 0.9 Dam sites 0.8 Gauges measured Gauges computed 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 50 100 150 200 250 300 350 400 450 Psum in mm 14 The extreme flood in August 2002 in the eastern part of the Ore Mountains and its statistical assessment z The hydrological event z Statistical evaluation of the flood event z How realistic is the statistical assessment ? 15 Characterisation of the inflow flood peaks in August 2002 in relationship to the assumed 1.000 and 10.000 yrs flood for 7 reservoirs in Saxonia Catch- Assumed Assumed Max. Max. Precip- Max. Max. Reservoir ment Design Design Inflow in Release itation in Inflow / Inflow / size Flood 1 Flood 2 August during the mm 1.000 10.000 in km2 HQ(1.000) HQ(10.000) 2002 flood in within yrs flood yrs flood m3/s m3/s m3/s August 48 h 2002 m3/s Lehnmühle 60.4 85.4 125 130 120 295 1.52 1.04 Klingenberg 90.4 90 150 160 150 314 1.78 1.07 Malter 130.5 147 200 220 220 251 1.50 1.10 Altenberg 6.8 9.2 11 7 7 392 0.76 0.64 Lichtenberg 38.4 39.2 60 60 48 228 1.53 1.00 Saidenbach 60.7 39.8 46 63 20 204 1.58 1.37 16 Return Period of flood peaks in August 2002, estimated on the basis of time series ending 2001 17 Uncertainty of statistical assessments of flood risks showing at the example of the flood in August 2002 in Saxonia Lichtenwalde / Zschopau 2000 Jahres-HQ-Werte AEV Jahres-HQ-Werte 1800 Reihe2 1600 1400 1200 1000 800 600 400 200 0 01234567T=500a Standardisierte Zufallsvariable y(T)=-ln(ln(1/Pu)) 18 Uncertainty of statistical assessments of flood risks showing at the example of the flood in August 2002 in Saxonia Lichtenwalde / Zschopau 2000 Jahres-HQ-Werte AEV Jahres-HQ-Werte 1800 Reihe2 1600 1400 1200 1000 800 600 400 200 0 01234567T=500a Standardisierte Zufallsvariable y(T)=-ln(ln(1/Pu)) 19 Uncertainty of statistical assessments of flood risks showing at the example of the flood in August 2002 in Saxonia Lichtenwalde / Zschopau 2000 1800 1600 1400 1200 1000 800 600 400 200 0 01234567 T=500a Standardisierte Zufallsvariable y(T)=-ln(ln(1/Pu)) 20 Modification of the flood statistics at the gauge Hainsberg 1/ Rote Weisseritz T bis 2001 mit 2002 350.00 Reihe 1928- 2001 2 12.74 11.91 Reihe 1928- 5 21.53 23.01 2002 300.00 T=2 a 10 28.11 34.46 T=5 a 20 35.07 50.06 25 37.41 56.25 T=10 a 250.00 50 45.1 80.15 T=20 a 100 53.47 113.33 T=25 a 200 62.62 159.46 200.00 T=50 a 300 68.36 194.43 T=100 a 500 76.03 249.31 1000 87.31 348.8 HQ in m3/s 150.00 T=200 a T=500 a 100.00 T=1000 a 50.00 0.00 0.0000 1.0000 2.0000 3.0000 4.0000 5.0000 6.0000 7.0000 y(T)=-ln(ln(1/Pu)) 21 The extreme flood in August 2002 in the eastern part of the Ore Mountains and its statistical assessment z The hydrological event z Statistical evaluation of the flood event z How realistic is the statistical assessment ? HQ Yearly floodvaluesat the gaugeDohna/Mueglitz River 100 150 200 250 300 350 400 50 0 1897 1899 1901 1903 1905 1907 1909 1911 1913 1915 1917 1919 1921 1923 1925 1927 1929 1931 1933 Period T Return 1935 1000 500 1937 200 1939 Jahres-HQ- Wert Jahres-HQ- Sommer-HQ- Wert Sommer-HQ- 1941 1943 1945 Jahr 1947 1949 Risk of3eventsin106 1951 1953 1955 1:5600 years 1:780 1957 1:571 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 22 23 Evidence of „record-breaking floods“ (Vogel et al. 2001) Yearly flood observations Counting of the highest flood peaks from the begin of observation with a yearly extension of the series Number of record breaking floods in a series of n years Probability of r record-breaking floods in a series of n years with S- Stirling‘s numberl Approximation for n>20 yrs 24 Number of „record breaking floods“ dependent on the starting point of the series in the Mulde River basin 14 Wechselburg1 Nossen1 12 Lichtenwalde Golzern1 Theoretische Anzahl in Abhängigkeit von der Reihenlänge 10 8 6 4 Anzahl der bisher beobachteten Höchstwerte beobachteten bisher der Anzahl 2 0 1900 1910 1920 1930 1940 1950 1960 1970 1980 Reihenbeginn 25 6000 Wechselburg/ Zwickauer Mulde Golzern Vereinigte Mulde 5000 4000 3000 HQ(1000) 2000 1000 0 1900 1910 1920 1930 1940 1950 1960 1970 1980 3500 Beginn der Reihe Lichtenwalde/ Zschopau 3000 Nossen/ Freiberger Mulde Effect of random 2500 samples on flood 2000 statistics, Dependency of the HQ(1000) 1500 1000 yrs- flood from 1000 the starting point of 500 the flood series 0 1900 1910 1920 1930 1940 1950 1960 1970 1980 Beginn der Reihe 26 3500 Pegel Golzern/ Vereinigte Mulde, Reihenbeginn1911 Pegel Wechselburg/ Zwickauer Mulde, Reihenbeginn 1910 3000 2500 2000 HQ(1000)- Wert HQ(1000)- 1500 1600 1000 Pegel Lichtenwalde/ Zschopau, Reihenbeginn 1939 1930 1940 1950 1960 1970 1980 1990 2000 2010 1400 Pegel Nossen/ Freiberger Mulde, Reihenbeginn 1926 Endpunkt der Beobachtungsreihe Effect of 1200 random 1000 samples on 800 flood statistics, Dependency of HQ(1000)- Wert 600 the 1000 yrs- 400 flood from the 200 ending point of 0 flood series 1930 1940 1950 1960 1970 1980 1990 2000 2010 Endpunkt der Beobachtungsreihe 27 Flood Levels since 1771 at an old building in the city of Grimma at the Mulde River in Germany, differentiated between winter and summer flood events 28 Seasonal Distribution of Catastrophic Floods in the history of the City of Zwickau between 1291 and 1835 Zwickau - Häufigkeitsauswertung historischer Hochwasser der Zwickauer Mulde gemäß Angaben aus der Stadtchronik (Zeitfenster: 1291 bis 1835) 25 20 15 Altstadt überflutet Häuser beschädigt Brücken beschädigt Monate 10 ohne Bauwerksschäden 5 0 Jan Feb Mär Apr Mai Jun Jul Aug Sep Okt Nov Dez Anzahl der Hochwasser 29 Example for a seasonal flood statistics Gauge Lichtenwalde/ Zschopau Pegel Lichtenwalde/ Zschopau 1400 Jahres-HQ- Werte bis 2001 Sommer-HQ unkorrigiert 1200 Winter-HQ unkorrigiert 1000 800 600 400 200 0 -2-101234567 30 Example for a seasonal flood statistics Gauge Lichtenwalde/ Zschopau Pegel Lichtenwalde / Zschopau