Combined Agro‐Hydrological and Flood Modeling Highlights Seasonal and Crop‐Specific Flood Regulating Ecosystem Services

Abstract

Flood‐Regulating Ecosystem Services (FRES) are widely used to assess the capacity of ecosystems in retaining water during a storm and mitigating hydrological extremes. Agriculture can play a role in the regulation of flood hazard, but the role of specific crop types in influencing flood regulation in small agricultural catchments remains largely unexplored. Indeed, FRES are typically evaluated by comparing the runoff generated in current conditions and a barren land scenario, treating agricultural land use uniformly in space (without distinguishing between crops) and time (without considering that agriculture has a seasonality). This study presents an approach to assess the seasonality of crop‐specific FLOod Regulating Agro‐Ecosystem Services (FLORAES). The proposed approach is based on coupling two fully distributed hydrological models: WATNEEDS, an agro‐hydrological model that estimates daily soil moisture based on agricultural water demand, and MOBIDIC, which uses the soil moisture conditions derived from WATNEEDS as the initial state to simulate flood hazards during extreme storm events. As a proof of concept for the methodology, we analyzed the upper part of the Ombrone Grossetano river basin (Italy), where agriculture plays a huge role in the local economy. Our results reveal that, under identical climatic conditions, different crops generate distinct initial soil moisture conditions, which can affect flood peak discharges. FLORAES don't contribute to flood mitigation in winter, whereas their contribution at the end of the growing season of each crop is not negligible, reaching the 20% of the peak discharge depending on the crop and the river basin size.