Application of hydrodynamics to assess coastal morphology to the north of Kelani River, Sri Lanka

Abstract

Studies on hydrodynamics are important since the hydrodynamic processes highly contribute to sediment transportation in the coastal regions. Erosion in Uswetakeiyawa coastal region of Sri Lanka has been a significant environmental issue since 2000. The Coast Conservation & Coastal Resources Management Department of Sri Lanka carried out artificial beach nourishment in 2012, and then a set of offshore breakwaters was constructed in 2013 to protect the nourished stretch of the beach. However, the beach was not developed to the desired extent. This research was carried out to assess hydrodynamics to forecast the noted coastal morphology in the Uswetakeiyawa coastal region. Wave data were gathered and analyzed using "SWELLBEAT" software for 12 months, covering both the monsoons. Further, "Delft3D" open source software was used to simulate the hydrodynamics in the study area, and seasonal changes of coastal morphology were analyzed for the study area using GoogleEarth images. The findings of this research indicated that due to the strong wave action perpendicular to the coast during the southwest monsoon, the beach was more vulnerable to erosion and there was no sediment transportation to the beach from longshore drift during inter-monsoon periods because sediments contributed from Kelani River were directly transported to the ocean. Also, the predominant sediment transportation to the study area was during the northeast monsoon.