Understanding the severe flood erosion and subsequent sedimentation in arid mountainous regions is crucial for assessing future flood risks under the pressure of global warming and human activities. It has long been hypothesized that a shift toward a more arid climate in an arid environment could enhance flood erosion despite the decreased discharge in rivers. However, the scarcity of long and reliable flood records makes testing this hypothesis difficult, thus limiting understanding of flood erosion during climate aridification. Here, we reconstruct a 1000-year-long extreme flooding record by exploring original Chinese historical archives and by analyzing sediment cores from the semi-arid mountainous catchment-Daling River estuary, NE Asia, based on the observation that instrumental floods normally cause coarse particle enrichment in the estuary. Our data reveal that on the centennial scale, extreme flooding mainly coincided with periods of climate aridification. The frequent rainstorms in this high variable topography catchment, coupled with reduced vegetation coverage as the climate shifts toward a more arid condition, have primarily contributed to the heightened flood erosion. Additionally, our record highlights the significant impact of accelerated reservoir construction and vegetation restoration in the river catchment since 1960 CE. These human activities have led to a noticeable reduction in coarse particle contents and sediment flux reaching the estuary which supports the previous viewpoints that human activities in Asia have greatly decreased river load entering the coastal oceans.