流域土地利用／覆被对洪峰的影响研究--以太湖上游西苕溪流域为例

The Influence of Land-Use and Land-Cover on Flood Peak——A Case Study of Xitiaoxi River Basin in the Headwater Region of Taihu Lake

土地利用/覆被变化是影响流域水文过程的重要因素。基于太湖流域在全国的重要性及太湖流域LUCC洪水效应研究的迫切性,选择太湖上游西苕溪流域为研究区,利用分布式水文模型HEC-HMS模拟5种土地利用/覆被情景下的2次典型洪水过程(5年一遇的台风型洪涝和5年一遇的梅雨型洪涝),定量区分单一土地利用/覆被对洪峰的影响程度。结果表明,对于同场降雨,5种土地利用/覆被情景下的洪峰流量大小顺序为:林地<疏林灌丛<草地<耕地<建设用地,峰现时间先后依次是建设用地、耕地、草地、疏林灌丛、林地。同样的土地利用变化对洪峰的影响程度,5年一遇的台风型洪水比5年一遇的梅雨型洪水反应剧烈。对洪峰流量影响最大的土地利用变化是其它用地变化为建设用地。对于同场降雨,5种土地利用/覆被情景下的洪水水文要素(洪峰流量、滞时)之间存在显著的定量关系。建设用地大大改变了洪峰形态,使流域原有的坦化洪水波形的能力降低,而林地则具有削减和延缓洪峰的作用。

Land-use and land-cover change is one of the main boundary conditions that influence many hydrologic processes. Owning to the importance of Taihu Lake Watershed and the imminence of study on the impacts of land-use and land-cover on flood, typical flood events of 5-year return period Plum rain flood and 5-year return period typhoon rain flood under five land use scenarios in Xitiaoxi River Basin in the headwater region of Taihu Lake are simulated by distributed hydrologic modeling system HEC-HMS. The influences of each land use type on flood peak are discussed. It is concluded that under the same rainfall events the order of peak flow produced by the five different land-covers are woodland 〈 shrub 〈 grassland 〈 arable land 〈 built-up land. Scenario of buih-up land is the first to reach peak flow, then arable land, grassland, shrub, and woodland. Flood peak responses under 5-year return period typhoon rain to the same land use change are more violent than that of 5-year return period Plum rain flood. The highest degree of impacts on flood peak of land cover change mode change from other land to built-up land. There are highly quantitative relationships between the peak flow and the lag times produced by the five different land-covers. Built-up land will reduce the basin＇ s ability of smoothing flood wave by changing flood peak remarkably, while forestland will mitigate and postpone flood peak.