Tasikoki Coastal Protection

Abstract

The beach adjacent to the Tasikoki Wildlife Rescue and Education Centre is one of the many beaches worldwide suffering from coastline recession. This loss of coast has a negative impact on the environment, local society and ecology. In general, shoreline retreat is caused by sea level rise (SLR) and erosion. The main objective of this research is to determine which factors are causing recession at Tasikoki beach and consequently which solution would be best in terms of mitigating coastline recession and protecting the hinterland from flooding. A Building with Nature (BwN) design philosophy has been considered to utilise natural processes instead of traditional ones, creating benefits for society and nature. Additionally, a model will be created in Unibest to substantiate and test the final solution.
The research first aimed to describe the coastal characteristics, ecosystem and societal system of the Tasikoki coast. This mainly consisted of a desk-study which was based on literature, but also of examining the surroundings and talking to locals. This study revealed amongst others the significant contribution of climate change on the shoreline retreat at Tasikoki beach.. Among the stakeholders, a major blocking power is absent. Nevertheless, an engagement plan is written to explain the local fishermen how they will benefit from the potential solution in order to prevent resistance. After gathering this general information to form a first impression, more location specific data was required to draw conclusions and setup the Unibest model. Every part of the required data has their own measurement method or source, using handmade measuring equipment, sonar GPS, sediment sieves and data retrieved from wind and wave models.
After a thorough analysis on the wave and wind climate and the surroundings of the Tasikoki coast, it could be concluded that the dominant wave direction is coming from a direction of 164˚ north. This determines the dominant sediment direction, which is thus propagating northward along the shore. Next, the direct coastal retreat due to SLR was calculated by using the Bruun-rule. Based on calculations and aerial image analyses, it was concluded that the two tidal inlets present at the Tasikoki coast play an important role in the erosion patternThe four main nearshore (CST) processes impacting the Tasikoki coast are wave impact, long waves, turbulence and avalanching/sliding. During the research, multiple possible solutions have been investigated which could mitigate the coastline recession. Based on a multi-criteria analysis, it was decided that a Biorock-based solution would suit the Tasikoki case best. This is a permeable submerged breakwater with a low current running through a steel frame to dampen waves and enhance nature at the same time.. A submerged breakwater was modelled in Unibest at Tasikoki beach. The result was positive. The structure traps sediment and causes more accretion along the coast than the length of the structure itself; functioning like a ‘sand engine’. At last a detailed implementation and monitoring plan was written, multiple scenarios are considered to make the solution more future-proof.