Response of flood regulation service to land use changes and dam construction-A case study in the Yangtze River Basin

Flood regulation service (FRS) is essential for a sustainable landscape and human society. It is not only subject to land use changes, but also affected by engineered measures (e.g., dam construction). However, the comprehensive impacts of the two major driving factors are still to be elucidated. To fill the research gap, this paper aims to evaluate the response of basin-scale FRS supply and demand to land use changes and dam construction. A case study in the Yangtze River Basin, China, shows that the 2020 FRS supply is mainly from land uses (84.85%) rather than dams (15.15%), with the biggest contributions from water bodies (rivers and lakes, 30.00%) and forests (29.35%). Between 1980 and 2020, the total FRS supply has increased by 10.50%, from 1.48 x 1010 m3 to 1.64 x 1010 m3. The net increase mainly comes from dam construction (84.65%) rather than land use changes (15.35%). Regarding the land use changes, the developed transfer matrix shows the ecosystem FRS flows and indicates that both the land use change amount and direction play a key role, e.g., the declines in farmlands have increased ecosystem FRS supplies when transiting into forest lands (by 3.68 x 108 m3) and water bodies (by 1.37 x 109 m3), while have decreased the ecosystem FRS supplies by -1.96 x 107 m3 with the transition into construction lands. These findings could shed light on the divergent roles between land-based measures and engineered measures in managing flood risk.