Abstract
This study quantifies the variations in wave characteristics and the resulting variations in potential longshore sediment transport rate along the coastline between Mount Lavinia and Negombo, Sri Lanka. Over the last 25 years, this coastal belt has been subjected to dramatic interventions due to the influence of rapid social-economic development in the country such as construction of the Colombo South Harbor jetty, ongoing Colombo Port City Project and mega sand dreading off Negombo coast. For the wave transformation, SWAN (Simulating Waves Nearshore) numerical model was applied, forced by offshore wave/wind. The Delft3D-FLOW model was used to estimate the longshore sediment transport rates and related morphodynamics using input reduction and morphological acceleration techniques. Results of the alongshore sediment transport capacity computations clearly indicate the variable characteristics of different parts of the study zone. The annual alongshore sediment transport capacity computed in the study area oriented northward, comply very well with the observations. The coastal belt between Mount Lavinia and Colombo, the wave climate, and subsequently the annual alongshore transport reached the highest values indicating a relative dynamic environment and there after decreased with a strong gradient northward. The explanation for these negative steep gradients and the environmental forcing/human interventions that govern the regional sediment transport are discussed in this paper.
Highlights
The ever-increasing economic and environmental considerations of coastal zones have provoked further studies of the variety of coastal processes such as coastal erosion, deposition and sediment transportation
This study quantifies the variations in wave characteristics and the resulting variations in potential longshore sediment transport rate along the coastline between Mount Lavinia and Negombo, Sri Lanka
The main contribution of this work is the quantitative determination of a nearshore wave climate, the alongshore sediment transport along 55 km long coastal belt between Mount Lavinia and Negombo
Summary
The ever-increasing economic and environmental considerations of coastal zones have provoked further studies of the variety of coastal processes such as coastal erosion, deposition and sediment transportation. Development within the coastal areas has increased interest in management of coastal erosion and restoration of coastal capacity to accommodate short- and long-term changes induced by human activities, extreme events and sea level rise. Often erosion is addressed locally at specific places or at regional or jurisdictional boundaries instead of at system boundaries that reflect natural processes. Human activities along the coast (land reclamation, port development, shrimp farming) and offshore (dredging, sand mining) in combination with these natural forces often exacerbate coastal erosion in many places and jeopardise opportunities for the coasts to fulfil their socio-economic and ecological roles in the long term at a reasonable societal cost. The Western and Southern provinces are linked by two of the country’s busiest highways and railway lines, touching the coast along most of their length (Garcin et al, 2008)
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