One of the territories most affected by flooding in Spain is the district of Vega Baja del Segura, located in the southernmost point of the province of Alicante. The objective of this article is to estimate the socio-economic and environmental efficiency of implementing sustainable urban drainage systems (SUDS) as part of the Vega Baja Nature Plan. This plan seeks to optimise rainfall management by reproducing and restoring the natural hydrological processes altered by the urban development of cities through integrated actions that generate new natural areas to be used and enjoyed by the residents. To this end, a cost–benefit analysis was carried out in accordance with the methodology established by the European Commission, and a social profitability of 4.3% (IRR) was obtained for the project, which shows the social benefit to be gained from its execution.