To assess the urban waterlogging mitigation effectiveness on low impact development (LID) in semi-mountainous regions, the Storm Water Management Model (SWMM) of a semi-mountainous region combined with GIS was generalized. The SWMM was calibrated and validated through maximum seeper depth of the checkpoints, and various LID scenarios have been designed according to local conditions. The discharge processes of outlets, surface runoff, peak flow and peak time were analyzed in different scenarios. The results show that: all the flow processes of outlets in the LID scenario are gentler than that in the status quo scenario, and the effectiveness of LIDs in semi-mountainous regions are different from that in plain regions because of the slope influence; in semi-mountainous regions, the LID effectiveness on surface runoff reduction decreases with the increase in rainfall return period or the extension of rainfall duration, but remains almost unchanged with the increase in rainfall peak coefficient; the LID effectiveness on control peak flow reduction is not remarkable with the change in rainfall characteristics, and the LID effectiveness on peak time delay is poor. This research can provide decision support for regional small-scale measures of urban waterlogging mitigation and reduction in semi-mountainous regions.

The source region of the Yellow River (SRYR) is continuously affected by climate change and human activities, and water security problems have long existed and are constantly changing, with the possibility of inducing a series of new risks. To diagnose the above problems and clarify their evolution features, based on the connotation of water security and its involved dimensions, this paper systematically reviews the relevant research results on water security in the SRYR, summarizes the water security problems and their evolution trend in the region from three aspects: water disasters, water ecology, and water supply security, and deeply analyzes the cascade effect of each water security problem. This paper provides a scientific basis for carrying out water disaster prevention and ecological restoration in the SRYR, which is conducive to optimizing the development and utilization of water resources in the context of adapting to climate change.