On how wetlands can provide flood resilience in a large river basin: A case study in Nenjiang river Basin, China

Wetlands are often acknowledged as a nature-based solution for improving flood resilience in a large river basin. However, the effects of wetlands on floods have not been assessed as extensively within a large river basin, as previous studies have mainly focused on assessing the effect on peak flows of a certain given return period. In this study, a distributed hydrological modeling platform was used to (i) quantify the effect of wetlands on floods with respect to event hydrographs, and (ii) investigate how flood regulation services can occur on the rising and falling limbs of an event hydrograph. Further, we hypothesized that flood resilience depends on the distribution and location of wetlands in the basin. The hydrological modeling study was conducted on a 297,000-km(2) large river basin in Northeast China, where wetlands are abundant covering approximately 12% of the basin area. Our modeling study show that wetlands can reduce peak and mean flows, event duration, and flow volume (i.e., runoff volume) by, respectively, 24% (12.14 mm), 12% (4.37 mm), 4% (1 day), and 17% (18 x 10(8) m(3)) in this large river basin. The attenuation efficiency of these wetlands varied with their location and size in the basin, especially apparent on peak flow, mean flow and flow volume on the rising limb of a flood event. These findings highlight flood regulation services and attest that wetlands can exhibit different effects; that sometimes they may amplify flood conditions. Thus, wetlands are an important land cover for enhancing resilience to flood events within large river basins, and wetland protection and restoration ought to be important conservation measures.