Climate feedbacks associated with land-use and land-cover change on hydrological extremes over the Yangtze River Delta Region, China

Quantifying how land-use and land-cover change (LULCC) drives extreme events is a priority to inform adaptation planning in a changing environment. Previous studies mainly focus on the effects of local LULCC on runoff generation processes; however, few on the effects of the climate feedbacks of LULCC. Here we couple the Variable Infiltration Capacity model with climate forcing from the Land Use Model Intercomparison Project, part of the new state-of-the-art Coupled Model Intercomparison Project phase 6, to synthetically detect global LULCC-induced impacts on hydrological extremes in one of the fastest developing areas in China and the world, i.e., the Yangtze River Delta (YRD). Results suggest that global LULCC increased extreme rainfall by 1.41 ∼ 3.90 % with spatial heterogeneity over YRD, especially during the rapid urbanization period. Regions with increasing extreme rainfall during the rapid urbanization stage match well with the city belt distribution, indicating the precipitation enhancement effects of the urban land surface. The combined impacts (with both LULCC and its climate feedbacks) lead to a 3.01–7.18 % increase in extreme runoff, much higher than the effects of LULCC only (0.05–0.14 %). The consistent signs of changes in extreme rainfall and runoff indicate the dominant role of LULCC-induced climate feedback in the changes in extreme runoff over the YRD region. In addition, flash droughts increased when considering the climate feedbacks of global LULCC, particularly during the rapid urbanization stage. LULCC tends to increase average flows, high flows, and low flows, particularly in an urban-dominated basin. When considering the climate feedback effects from global LULCC, the LULCC would lead to a larger increase in high flows and average flows, thus floods. We highlight a need to consider land–atmosphere interactions in addition to land-surface processes in projecting changes in hydrological extremes.