鉴于小流域山洪具有突发性,预警指标确定难度较大。以庙下溪小流域为例,提出基于HEC-HMS分布式水文模型的小流域设计洪水计算方法,并运用水位流量反推综合确定山洪雨量预警指标。结果表明,该方法的设计洪水计算结果与浙江省推理公式、瞬时单位线计算结果相差不大,与实际的山洪灾害降雨资料也较吻合,可见其确定的雨量预警指标基本合理,HEC-HMS模型在山洪雨量预警指标确定中具有可行性。 In view of the sudden flood in the small watershed, the early warning index is difficult to determine. Taking Miaoxiaoxi small watershed as an example, this paper proposes a calculation method of small watershed design flood based on HEC-HMS distributed hydrological model. The results show that the calculated result of design flood of this method is not much different from the result calculated by Zhejiang Province’s reasoning formula and instantaneous unit line and is consistent with the actual rainfall data of flood disasters. It can be seen that the indicator of rainfall early warning is basically reasonable. The HEC-HMS model It is feasible to determine the forewarning index of flash flood.