Spatial and Temporal Patterns in Nonstationary Flood Frequency across a Forest Watershed: Linkage with Rainfall and Land Use Types

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Understanding the response of flood frequency to impact factors could help water resource managers make better decisions. This study applied an integrated approach of a hydrological model and partial least squares (PLS) regression to quantify the influences of rainfall and forest landscape on flood frequency dynamics in the Upper Honganjian watershed (981 km2) in China. The flood events of flood seasons in return periods from two to 100 years, wet seasons in return periods from two to 20 years, and dry seasons in return periods from two to five years show similar dynamics. Our study suggests that rainfall and the forest landscape are pivotal factors triggering flood event alterations in lower return periods, that flood event dynamics in higher return periods are attributed to hydrological regulations of water infrastructures, and that the influence of rainfall on flood events is much greater than that of land use in the dry season. This effective and simple approach could be applied to a variety of other watersheds for which a digital spatial database is available, hydrological data are lacking, and the hydroclimate context is variable.