Biwa Lake Basin. Katsura River Basin. Seta/Uji River Basin. Kizu River Basin. Hiyoshi Dam. Katsura Nouso. Setagawa Dam Amagase Dam Takayama Dam

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1 48 B 17 4 Annuals of Disas. Prev. Res. Inst., Kyoto Univ., No.48 B, 25 Λ Λ : 1. ( 24) 1

2 (Table 1 ) Hiyoshi Dam Biwa Lake Basin Katsura Nouso Mukaijima Hirakata Kamo Ieno N Katsura River Basin Dams Simulation Targets 2 km Seta/Uji River Basin Kizu River Basin Setagawa Dam Amagase Dam Takayama Dam Nunome Dam Hinachi Dam Shorenji Dam Murou Dam Fig. 1 Yodo River basin with the location of dams and analysis target points. 2. (8,24km 2 ) 2 4 ( 67km 2 ) (3,848km 2 ) (1,596km 2 ) (56km 2 ) (1,1km 2 ) (87km 2 ) (383km 2 ) 6 7,281km 2 ( ) (Fig.1) km 2 ( 1995) 4 ffl ffl ffl ffl km km ( 21) 5. ( 24)

3 Table 1 Properties of dams located in the Yodo River basin. Operation Catchment Total Flood cont. Λ Flood cont. Pre-release Dam start area volume capacity method [year] [km 2 ] [1 6 m 3 ] [1 6 m 3 ] Setagawa 195 ΛΛ ΛΛΛ Constant No Amagase Constant Yes Takayama Fixed disc. rate No ΛΛΛΛ Shorenji Constant Yes Murou Constant Yes Nunome Fixed disc. rate No Hiyoshi Constant No Hinachi Constant No Λ Capacity from Limited Water Level to Surcharge Water Level ΛΛ Nango dam is completed in 195. Current Setagawa dam is completed in ΛΛΛ Capacity ofbiwalake from standard water level (-.3 m) to designed high water level (1.4m) ΛΛΛΛ Pre-release can be conducted in non-flood season Fig. 2 Schematic diagram of the soil layer (a) and stage-discharge relationship (b) of saturatedunsaturated subsurface and surface rainfallrunoff model. ( 24) m ( 24) D [m] d s [m] d c [m] (Fig. 2 ) k c [m/s] k a [m/s] v c = k c i v a = k a i q [m 2 /s] h[m] q = 8 >< >: v c d c h d c fi ; (» h» d c ) v c d c + v a (h d c ); (d c <h» d s ) v c d c + v a (h d c )+ff(h d s ) m ; (d s <h) (1) fi [-] fi = k a =k c q h Fig. 2 (b) c [m/s] 8 c = (2) v a ; (d c <h» d s ) >: mff(h d s ) m 1 + v a ; (d s <h) fiv c h d c fi 1 ; (» h» d = r(t) 3

4 Ordinary operation Operation under flood warning Preliminary release operation Peak attenuation operation Emergency operation Post flood operation Surcharge Water Level Flood Release Water Level Normal Water Level for non-flood season Normal Water Level for flood season Minimum Permissible Water Level Daily rainfall data observed from year 19 to , 1, 15 and 2 year quantiles of two days average rainfall over each catchment Hourly rainfall data observed from year 1982 to 21 Spatial and temporal distributions of hourly rainfall in the Yodo River basin Ten largest rainfall events with two days duration for each catchment Flood warning Fig. 3 Operation statuses and specified water levels of dam operations model. Enlarge the ten ovserved hourly rainfall events to correspond to 5, 1, 15 and 2 quantiles Simulate hydrographs for each catchment with all the enlarged rainfall events with and without dam effects (3) r(t) [m/s] 1982 ( 24) n =.6m 1=3 s D =1.m d s =.2m d c =.1 m k a =.1 m/s fi =8. n = 1. m 1=3 s n =.3 m 1=3 s (1) d c d s ( 1999) ffl ffl ffl ffl ffl ffl 6 Fig. 4 Flow of analysis. if-then Fig. 3 ( 24) ( ) ( ) Fig. 4 Fig

5 Table 2 Best distributions, Goodness-of-fit, and T -year two days rainfall. Target Area Probability Goodness-of-fit T -year quantiles [mm] catchments [km 3 ] distribution SLSC COR Hirakata 7281 Gumbel Kamo 1469 Gumbel Nouso 1114 Gumbel Katsura 833 GEV Mukaijima 4153 Gumbel Ieno 475 Gumbel (1) () 99 ( 1974) (2) ( ) (21) SLSC ( 1986) COR Gumbel GEV Gumbel GEV SLSC.3 COR.99 ( 1998) Gumbel GEV 6 Gumbel GEV Table ( ) () 1.5 km

6 Hirakata 14 Kamo Simulated peak discharge [m 3 /s] Ave. without dam without dam Ave. with dam with dam Capacity Return period [year] Simulated peak discharge [m 3 /s] Ave. without dam without dam Ave. with dam with dam Capacity Return period [year] Fig. 5 Return periods of two days rainfall and simulated peak discharge without and with dams at Hirakata. Fig. 6 Return periods of two days rainfall and simulated peak discharge without and with dams at Kamo Fig , m 3 /s Fig km km ( ) ( ) 6

7 Sim. peak discharge with dams [m 3 /s] Capacity Kamo Discharge [m 3 /s] Discharge at Kamo without dams Discharge at Kamo with dams Inflow at Takayama dam Outflow at Takayama dam Time [h] Sim. peak discharge without dams [m 3 /s] Fig. 9 Same as Fig. 8 but based on rainfall events in Fig. 7 Simulated peak discharge at Kamo without dams (x-axis) and with dams (y-axis). Discharge [m 3 /s] Discharge at Kamo without dams Discharge at Kamo with dams Inflow at Takayama dam Outflow at Takayama dam Time [h] Fig. 8 Simulated discharge at Kamo without / with dams and simulated inflow / outflow at Takayama dam; Input data is enlarged based on rainfall events in (1) Fig. 7 1:1 Fig m 3 /s 9 m 3 /s m Fig m 3 /s 42 % (= 615 km 2 / 1469 km 2 ) 6 m 3 /s 7

8 Sim. peak discharge with dams [m 3 /s] Capacity Nouso Discharge [m 3 /s] Discharge at Nouso without dams Discharge at Nouso with dams Inflow at Hiyoshi dam Outflow at Hiyoshi dam Time [h] Sim. peak discharge without dams [m 3 /s] Fig. 1 Simulated peak discharge at Nouso without dams (x-axis) and with dams (y-axis). Fig. 11 Simulated discharge at Nouso without / with dams and simulated inflow / outflow at Hiyoshi dam;input data is enlarged based on rainfall events in Fig m 3 /s Discharge [m 3 /s] Discharge at Nouso without dams Discharge at Nouso with dams Inflow at Hiyoshi dam Outflow at Hiyoshi dam Time [h] Fig. 12 Same as Fig. 11 but based on rainfall events in m 3 /s 61 m 3 /s (2) 1 26 % 5 42 % Fig m 3 /s Fig m 3 /s 15 m 3 /s 8

9 1 m 3 /s 1 m 3 /s Fig Fig Fig. 9 Fig m 3 /s 9 m 3 /s m 3 /s ( ) ( ) ( flood/geohymos) (CREST)( ) , pp No. 691 / II-57 pp , pdf/treport_vol_12-8.pdf B pp

10 pp B-2 pp Vol. 11 No. 7 pp pp Analysis of dam effects on flood control in the Yodo River basin with a distributed rainfall-runoff prediction system Takahiro SAYAMA, Hiroki KANNO Λ,Yasuto TACHIKAWA, and Kaoru TAKARA Λ Graduate School of Engineering, Kyoto University Synopsis The effects of dams on flood control were analyzed at several locations in the Yodo River basin using a distributed rainfall-runoff prediction system including dam operation models. Input rainfall distributions for the analysis were created by multiplying some factors to ten observed rainfall patterns to adjust them to be 5, 1, 15 and 2 year return periods in terms of two days rainfall in a catchment. The system simulates discharge with and without taking into account the effects of dams for the all created input rainfall. The comparisons of simulated peak discharges indicated that at Kamo, whose catchment contains Takayama dam at the middle reach, there is a certain range of natural peak flow thatcanbe attenuated effectively to the allowable maximum discharge. On the other hand, at Noso, whose catchment contains Hiyoshi dam at the upper reach, peak discharge were attenuated relatively constantly regardless the natural peak flow. Keywords :distributed rainfall-runoff model, Yodo River basin, dam, flood control effects 1