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

Abstract

This study evaluates the historical coastal change and development along the eastern coastline of the Upper Gulf of Thailand between 1953 and 2019 based on a series of aerial photographs and satellite images. Long-term ($70 years) and short-term ($10 years) shoreline movement rates were analysed using the Digital Shoreline Analysis System (DSAS). Results of this analysis indicate that the shoreline along the western coast (WBK) of the Bang Pakong River mouth has undergone severe coastal degradation, with a land loss of about 980 ha over the last seven decades. Meanwhile, the eastern coastline (EBK) has developed continuously over this time span, resulting in a land growth of about 552 ha. Based on historical shorelines recorded since 1954, the shoreline recession along the WBK coast accelerated over five decades. The average shoreline change rate reached approximately À9 m/year in 2002 and is shown to be related to land subsidence, which was due to groundwater

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

“…Since the shoreline responded to the existing sand sausages without a systematic trend, other factors may outweigh their effectiveness. Because a high rate of land subsidence was reported in this area during 1992-2015 14,37 , the unsuccessful use of sand sausages on coastal stabilization may be caused by that very high rate of land subsidence (up to 6 cm/y). Another possible factor responsible for the ineffectiveness of sand sausage during 2002-2010 can be the settlement of the structure combined with sand leakage from their geocontainers resulting in lowering the level of the breakwater's crest 34 .…”

“…According to our horizontal shoreline change results, the seawall constructed near the Chao Phraya River mouth in 1994 has successfully stabilized about 23% of the ECPD coastline. The remaining unprotected coastline still underwent severe shoreline recession during 1954-2013 due mainly to land subsidence caused by groundwater extraction 14,27 . This study evaluated the e cacy of the grey and green/nature-based solutions applied along the ECPD coastline using two approaches.…”

“…Figure 4a indicates that the rubble-mound-submerged breakwaters caused higher rate of shoreline advance and lower rate of shoreline retreat than the sand sausage, even though they have similar functions. The rubble-mound breakwater's higher effectiveness than sand sausage may be related to the relatively lower rate of land subsidence, which varied only between 1.0-2.5 cm/y during 2000-2015 14 combined with the durability of the rubble mound (> 10 y).…”

“…S2b and 3). In 2019, bamboo fences were applied near the BPK River mouth, where land subsidence may dominate the shoreline retreat in this area 14 , yet the recession of the mangrove shoreline has persisted to present. With a low sedimentation rate combined with the short-life span, bamboo fences are not the best choice for stabilizing shorelines when the subsidence rate is higher than the sediment deposition rate.…”

“…During the past century, signi cant coastal degradation due to shoreline retreat has been reported worldwide [1][2][3][4][5][6][7][8][9][10][11] . Shoreline recession found around the world is dominated by several factors such as sealevel change [6][7][8] , storm surge 12 , land subsidence 13,14 , and coastal development 15 . Since shoreline change can cause negative impacts not only on human lives and societies but also on coastal environments, many coastal protection measures, either grey/hard or green/nature-based solutions, have been applied to mitigate the adverse effects.…”