Evaluation of beach nourishment in Mar del plata, Argentina: An application of the CoastSat toolkit

Sandy coasts play a crucial role in various human activities and support the economies of many coastal states. Due to their importance, coastal erosion mitigation techniques are often implemented. Among these techniques, beach nourishment is considered an environmentally acceptable method for coastal protection and restoration. In this work, a methodology for the evaluation of such projects is proposed and applied to the biggest beach nourishment project in the city of Mar del Plata, Argentina. The nourishment was carried out between 1998 and 1999 in Playa Grande (PG), Varese (V) and Bristol (B) bays. The CoastSat toolkit was implemented to obtain shoreline positions from satellite imagery and to derive a 36-year monthly time series of beach width in the region. For the analysis, three distinctives time lapses are identified: pre-intervention, response, and new equilibrium. An exponential decay function was fitted to determine the response lapse and its characteristics. Metrics such as mean beach width and trends were computed and used to compare the condition of beaches before and after the project. Results show that the region experienced a net growth after nourishment, with beach width doubling in Bristol and Playa Grande, and increasing tenfold in Varase. Nourishment did not alter the erosive trends of Playa Grande and Bristol, nor the growth trend of Varese. Regarding renourishment planning, according to our findings, for Playa Grande and Bristol beaches to achieve a net growth of 1 m, it would require the deposition of 17 m³ of sediment per meter of coastline. This study highlights the suitability of the CoastSat toolkit for assessing the effectiveness of beach regeneration.