Performance forecasting for the beach nourishment project at Palliyawatta-Uswetakeiyawa Sri Lanka

Abstract

Beach nourishment is a soft engineering solution that is increasingly used to combat erosion in a sustainable manner. Sri Lanka's first major Beach nourishment project was carried out over a 1.8 km stretch in the UswetakeiyawaPalliyawatta area, by the Coast Conservation Department of Sri Lanka (CCD). The Project was conducted in January 2012 and 300,000 cubic meters of offshore sand pumped using a dredging vessel was used to nourish the stretch of eroded beach with a total project cost of USD 300 million. This research was carried out to assess the performance and to forecast the future performance of the above nourishment project. Topographic data and grain size data were gathered and analyzed over a period of six months spanning an entire seasonal cycle. Satellite imagery spanning a much larger time period were also analyzed and complemented with the field data. The findings of the research indicate that due to incorrectly oriented sand retention structures and the incorrect grain size of nourished sand, the nourished area is currently undergoing rapid erosion. However, it is forecasted that the beach will come back to its pre-nourished stage after a period of 12 months. This will result in the exposure of a beach rock at the mean sea level and will cause the beach to lose its recreational and aesthetic value, and to prevent this and to retain the nourished sand, the correct orientation of the retention structures and the appropriate grain size for nourishment are proposed.