| Under the influence of infrastructure construction, industrial and agriculturalproduction, ecological environment construction and other human activities, theunderlying surface of Haihe River Basin has changed, which led to the variation ofdesign flood accordingly. So it is necessary to revise the parameters of reservoirinflow design flood after the underlying surface conditions change in order to adjustmethods and layouts of flood control projects.Base on the Haihe river basin, this study analyzed the revising methods of thedesign flood under the change of underlying surface and revised the design flood ofDaqinghe river basin. The main content and results are as follows:(1) Statistics of flood data in the typical regions. Typical flood events wereselected, rainfall and runoff data in every flood event were extracted including totalrainfall, peak flow, flood volume, runoff, surface runoff, antcedent precipitation andso on.(2) Base on the long-term hydrological observation data, the trends ofprecipitation and runoff were analyzed using Spearman test，Mann-Kendall test andmoving average. Break points were detected by sequential clustering method,smoothing F test and double mass curve. According to the results, the precipitationand peak flow in two reservoirs both showed a decreasing trend and the break pointwas1979.(3) The correlation analysis of precipitation and runoff and the forward restoreof flood. Runoff producing parameters such as maximum storage capacity,evaporation from water surface and soil moisture content were analyzed and thecorrelation analysis between precipitation and runoff was done before and after thebreak point. The relationship between precipitation and runoff before1980wasrevised by that after1980. So the influence on flood volume of changing underlyingsurface was studied and the time series of flood volume was restored. Correlationdiagrams in different periods were plotted and the variation of flood peak wasestimated according to flood volume, thus the time series of flood peak was restored.(4) The compute of design flood process. The design flood was computedaccording to frequency analysis of flood before and after revise. The results showedthat the flood peak and flood volume both showed a decreasing trend due tounderlying surface changes especially those caused by water conservancy projects and converting cultivated land into forests. In addition, the flood peak and floodvolume of small floods reduced more than big ones, which conformed to the rule thatunderlying surface changes played a more important role in regulating small floodthan big floods. |
