Rehabilitation of the fishery harbour of Dodanduwa

Abstract

Dodanduwa is a small fishery village in the south-west of Sri Lanka, about 20.000 inhabitants are dependent on the fishery industry. Currently the harbour facilities, that were constructed in 2009, are hard to reach due to the wave conditions and sedimentation at the harbour entrance. The Ministry of Fisheries and Aquatic Resources Development initiated a rehabilitation project in 2015. In this report the issues at the Dodanduwa harbour area are thoroughly investigated and conceptual solutions are presented. The goal of this report is to provide several durable and feasible conceptual designs for the fishery harbour of Dodanduwa; which fulfil the needs of the community on the longer term, taking the socio-economic and environmental effects into account. This goal is reached by answering five sub questions: 1. What does the coastal system look like? 2. What is causing navigability issues at the harbour? 3. What are the involved parties and what are their interests? 4. What is the impact of the improved harbour on the surrounding area? 5. Which requirements should be considered when designing the harbour improvement? The report is divided into three parts: the preliminary study, the conceptual design and the evaluation. In 2009 the first major adjustment has been made to the Dodanduwa fishery harbour, a breakwater was constructed at the northern bay. The breakwater was only partly constructed, resulting in a less safe situation in the harbour. The redevelopment plans of the harbour involve ensuring safe navigation inside the harbour area and enough accessible anchorage capacity for the coming 10 years. To solve the issues in the Dodanduwa harbour on the long term, five different conceptual designs are presented. At the end of the design phase some recommendations are given. Six general recommendations are presented, closing with separate recommendations for the design of the hydraulic structures. Before continuing with the final design the expected future fleet should be investigated more thoroughly. Large uncertainties in the expected future fleet may lead to a non-functional harbour improvement. Another uncertainty is the effect of an all year open river mouth; with stakeholder interviews and research on salt water intrusion this should be cleared out. For a better prediction of the impact of the hydraulic structures on the coastline, performing wave and sediment modelling provides more insight. The extension of the current breakwater must be further investigated, the safety level of the current breakwater must be determined. The transition between the current breakwater and the new breakwater may not lead to a weak spot. The current preliminary designs are based on several assumptions due to data limitations. For the final designs it is strongly recommended that all investigations, such as bathymetry measurements and soil investigations, are performed properly. The financial feasibility of the project is uncertain, multiple fishery harbours in the region are already constructed. A study to determine total life cycle costs must be performed to determine the financial feasibility.