Numerical simulation of detached breakwaters for mangrove restoration in Bengkalis Island, Indonesia

Mubarak Mubarak,Alvin Defarian,Sigit Sutikno,Koichi Yamamoto,Keisuke Murakami,M Olivia,D Wishart,G Wibisono,I.M Agus Ariawan,D Andrio,A Marto,R Ridwan,I.D Ketut Sudarsana,M Infantri Yekti,K Yamamoto,E Saputra,G Pringgana

doi:10.1051/matecconf/201927604005

Abstract

This paper presents the application of detached breakwater to reduce wave energy for protecting mangrove planting site. Initial planting of mangroves still needs seawater for their growth, but they will be distracted by the big wave. How is the detached breakwater should be designed for this purpose is the objective of this research. This research simulated the wave propagation at the existing condition and under some alternative designs of detached breakwater to find out the optimum design of detached breakwater for mangrove planting site. The CADMAS-SURF is a numerical model that was used for the simulation. Bengkalis coast in Indonesia was picked up as study area of this research. The mangrove degradation and the severe coastal abrasion have occurred in this area for long period. The simulation result shows that in the high tide condition, the wave height and wave velocity at the mangrove plantation area are about 1.12 m and 3.86 m/s respectively in the case of the existing condition. In this case, the initial mangrove plantation cannot be applied because it will be destroyed by the wave. By applying breakwater both for rubble mound type and vertical wall type, the wave height and the wave velocity were reduced to 0.69 m, 2.39 m/s and 0.72 m, 2.31 m/s respectively. In this case, the initial mangrove plantation can be applied because it will not be destroyed by the wave.

Highlights

The islands of Riau province which are located at Malacca strait, are mostly covered with peatland as presented in Fig. 1a [1]
Temporal LANDSAT image analysis clarified that the peatland area decreased at about 160 ha/year in the Riau Province on average because of the coastal erosion (Fig. 1b) [3]
Bengkalis sea level tides used for tidal analysis are measurement data obtained from the Hydrographic Center and Navy-Marine Oceanography, Indonesian Army on August 22nd to September 5th, 2015

Summary

Introduction

The islands of Riau province which are located at Malacca strait, are mostly covered with peatland as presented in Fig. 1a [1]. The coastal setback in Bengkalis Island, one of the Riau Islands is up to 30 m/year [4, 5] This coastal peat erosion endangers the local community life and https://doi.org/10.10 51/matecconf /201927604005 plantation activity in the coastal area and is recognized to the Bengkalis Regency, Riau Province. The bog-burst is one kind of peat failure It happens in the wet season, when the unusual high groundwater table maintained because the waterways of the plantation are constructed near the coastline, and the water level is maintained high for oil palm bunch transportation. The coastline setback endangers the coastal communities as well as agricultural activities

Objectives

Methods

Results

Conclusion