Response of different vegetation cover to different design rainstorm patterns in the watersheds
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Abstract:
The global warming trend has intensified,increasing the frequency of heavy rain disasters in China,making the mountain watershed easy to produce flash floods.Rain pattern was one of the influencing factors of mountain torrent disaster.Applying the designed rainstorm pattern to watersheds with different vegetation coverage rates in mountainous areas may help to analyze the impact of design rainstorm patterns in different return periods in watersheds.Thus it is important to reveal the response law of different vegetation coverage basins in mountainous areas to different rainstorms,and provide technical support for a more reasonable analysis of mountain rainstorms and floods. The Dayi,Guankou,and Hanwangchang watersheds in Sichuan Province were taken as the study area,and the spatio-temporal variable source mixed runoff generation model was used.The runoff coefficient,flood peak modulus,average runoff coefficient,and average flood peak modulus were used to design rainstorms for different return periods.Analysis of the hydrological process was formed by precipitation under different vegetation coverage in the watershed under different vegetation conditions. In the three small watersheds of Sichuan Province simulated by the spatio-temporal variable source mixed runoff generation model,the simulation accuracy evaluation index values were within the allowable range,indicating that the spatio-temporal variable source mixed runoff generation model was suitable for flood process simulation in small mountain basins.The runoff coefficient and flood peak modulus showed different characteristics under different return periods and different design rainstorm conditions.Under different return period conditions,the rainfall patterns in the basin show a decreasing trend from the front type,the middle type to the rear type,and the flood peak modulus is increasing.Under different rainstorm designs conditions,the runoff coefficient first increases and then decreases slightly and then tends to a stable state under increase of the return period,and the flood peak modulus increases with the increase of the return period. The watersheds with different vegetation coverage respond differently to the designed rainstorm patterns in different return periods,and the watersheds with higher vegetation coverage have smaller runoff coefficients and flood peak modulus.Under different return periods and different design rainstorm conditions,the runoff coefficient and flood peak modulus present different characteristics,which have a certain impact on the formation of runoff in the basin.In the Guankou basin,its peak discharge and peak emergence time show a certain trend with the increase of the return period and the different design rainstorm patterns.Observing the changes in the flooding process under different recurrence periods and different design rainstorm conditions is of great significance for mastering the law of storm floods in mountainous areas.
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