Impacts of Long Jetties Construction on Shoreline Change at the Western Coast of the Gulf of Thailand

Abstract

Pranburi Jetties, a pair of long jetties with a length of 800 m and 860 m, have been constructed at the Pranburi River inlet, located on the western coast of the Gulf of Thailand since 1999 to stabilize the river mouth. The purposes of this study were to evaluate the responses of shoreline due to the construction of Pranburi Jetties, and the accuracy of the One-Line model (OLM) on predicting the shoreline change due to construction. Based on the shoreline positions retrieving from aerial photographs and satellite imagery during 1967-2018, the difference in shoreline evolution before and after the construction of the jetties was evaluated using ArcGIS and Digital Shoreline Analysis System. The predicted shorelines using the One-Line model were compared with the image-analyzed shorelines for evaluating the accuracy of the model. The results indicated that the construction of Pranburi Jetties had caused the shoreline accretion at the vicinity of the jetties with the maximum accretion of up to 300 m in 2018. The land growth of 16.2 and 9 ha took place at the northern and southern coasts, respectively. The percentage of errors between the predicted and the imageanalyzed shoreline varied from 2 to 13,000 percent with an average of 250 percent. Misprediction in shoreline change using a numerical model caused unnecessary construction of three detached breakwaters at the northern coast of the jetty.

Seven decades of shoreline changes along a muddy mangrove coastline of the Upper Gulf of Thailand

“…In addition, the typical shoreline definition cannot be used for identifying non‐natural shorelines where there are artificial beaches and developed coasts with engineered structures. We represented artificial shorelines by the alignment of identifiable coastal structures such as roads, bridges, dikes, and seawalls (Besset et al, 2019; Bidorn & Rukvichai, 2018; Bidorn et al, 2020; Phanomphongphaisarn et al, 2020). Since the BPK coasts are bounded by both mangrove forests (natural as well as replanting mangroves) and engineered coastal structures, vegetation edges and boundaries of coastal stabilization structures were used as shoreline proxies along the coast.…”

“…The positional errors include shoreline proxy offset ( E o ), tidal fluctuation ( E t ), seasonal variation ( E s ), rectification error ( E r ), digitizing error ( E d ), pixel error ( E p ), and toposheet survey error ( E ts ) (Ding et al, 2019; Kankara et al, 2015; Morton et al, 2005; Santos et al, 2021). Since shoreline positions were extracted from an image file (.tiff) of aerial photographs and satellite images using vegetation lines and alignment of coastal structures as shoreline proxies, the shoreline position uncertainties are mainly related to resolution of the material and orthorectification or georeferencing process (thus, the terms E o , E t , E s , E d , and E ts can often be neglected; Gibbs et al, 2015, 2019; Phanomphongphaisarn et al, 2020). The positional uncertainty ( U sp ) was determined using Equation (Gibbs et al, 2019; Hapke et al, 2006, 2010; Santos et al, 2021), and the image resolution and root mean square error (RMSE) due to the georeferencing process for each year’s dataset are presented in Table 1.…”

Effectiveness of grey and green engineered solutions for protecting the low-lying muddy coast of the Chao Phraya Delta, Thailand

“…The shoreline positions in this study were obtained from an image file (TIFF format) of aerial photographs and satellite imagery; position uncertainties are then mainly related to the resolution of the materials and orthorectification or georeferencing processes. Then the terms E o , E t , E s , E d , and E ts can often be neglected 46 , 51 . Shoreline change rate uncertainty ( U i ) is typically quantified as the quadrature sum of uncertainties for the shoreline position each year, divided by the number of years between the first and last shoreline 14 , 51 .…”

Effectiveness of grey and green engineered solutions for protecting the low-lying muddy coast of the Chao Phraya Delta, Thailand

“…The shoreline positions in this study were obtained from an image le (TIFF format) of aerial photographs and satellite imagery; position uncertainties are then mainly related to the resolution of the materials and orthorecti cation or georeferencing processes. Then the terms E o , E t , E s , E d , and E ts can often be neglected 44,49 . Shoreline change rate uncertainty (U i ) is typically quanti ed as the quadrature sum of uncertainties for the shoreline position each year, divided by the number of years between the rst and last shoreline 14,49 .…”