A 400-metre fishery pier on Thailand’s Ban Khlong Wan coastline was followed by dramatic changes in the shape and composition of the shore, with one section of beach advancing by as much as 250 metres.
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section → follow → metres
The findings come from a study published in Scientific Reports on August 22, 2025, titled
Unintended coastal transformation from small-scale infrastructure and land use change.
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findings → come → change
Researchers combined historical shoreline records, high-resolution LiDAR observations, beach sediment analysis and upstream land-use data to reconstruct how the coastline changed between 1966 and 2023.
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coastline → combine → 1966
They found that the pier disrupted the movement of sand along the coast, while changes upstream contributed additional fine sediment.
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changes → find → sediment
The result was not a simple story of erosion caused by coastal structures.
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result → cause → structures
Instead, the researchers found that infrastructure, sediment transport and changes to wetlands and aquaculture interacted to transform different sections of the coastline in different ways.
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infrastructure → find → ways
The coastline was relatively stable before the coastal development
The researchers analysed shoreline positions along the Ban Khlong Wan coastline from 1966 to 2023, dividing the record into a pre-development period from 1966 to 2002 and a post-development period from 2002 to 2023.
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researchers → analyse → 2023
The study area was divided into the 1.5-kilometre Khlong Wan coastline in the north and the 5-kilometre Wa Ko coastline in the south.
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area → divide → south
Before the coastal development, the Khlong Wan coastline experienced substantial retreat.
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coastline → experience → retreat
Table 1 shows that 82.5% of the Khlong Wan transects were classified as retreating, with a mean shoreline change rate of −0.28 metres per year.
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% → show → year
The researchers summarised this by stating that 83% of the area was eroding at an average rate of approximately −0.3 ± 0.08 metres per year.
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% → summarise → year
Table 1 shows that 39.4% of the coastline was stable and 33.3% was accreting.
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% → show → coastline
Several structures were introduced during the broader 2004 to 2008 development period.
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structures → introduce → period
These included a 400-metre fishery pier and a 700-metre breakwater.
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These → include → pier
Twelve detached breakwaters were constructed by the Harbour Department in 2007 and 2008, while Khlong Wan Municipality constructed a seawall in 2005 for a public park.
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Municipality → construct → park
The 400-metre pier trapped sand on one side
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pier → trap → side
The most dramatic shoreline change occurred along the Wa Ko coastline, south of the pier.
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change → occur → pier
Within 400 metres of the structure, the shoreline advanced by as much as 250 metres, corresponding to an accretion rate of approximately 12 metres per year.
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shoreline → advance → year
The researchers estimated that the resulting land accretion covered approximately 40,000 square metres.
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accretion → estimate → metres
They attributed this primarily to the pier interrupting longshore sediment transport and trapping sand on its updrift side.
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pier → attribute → side
The pattern also supported the researchers’ conclusion that sediment was predominantly moving from south to north along this stretch of coastline.
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sediment → support → coastline
The shoreline position data show that the seaward advance associated with the pier stopped by 2021.
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advance → show → 2021
The researchers suggested that the sediment-trapping capacity of the pier may have reached an equilibrium after about 13 years.
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capacity → suggest → years
Table 1 records a maximum shoreline movement of 250 metres for the Wa Ko coastline during the post-development period.
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Table → record → period
The northern coastline responded differently
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coastline → respond → ?
The Khlong Wan coastline showed a markedly different pattern after construction.
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coastline → show → construction
Its mean net shoreline movement was 18 metres, while shoreline change rates ranged from −0.16 to 3.67 metres per year according to Table 1.
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rates → range → Table
The table records accretion across 96.8% of the Khlong Wan coastline during the post-development period.
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table → record → period
The paper's text rounds this figure to 97%.
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text → round → %
Before development, by comparison, only 8.0% of the Khlong Wan coastline was classified as accreting, while 82.5% was retreating.
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% → classify → coastline
Part of the later shoreline advance was associated with deliberate sand placement.
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Part → associate → placement
The Harbour Department added approximately 90,500 cubic metres of sand as an erosion-control measure.
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Department → add → measure
This means the post-development changes along Khlong Wan cannot be attributed to the coastal structures alone.
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changes → mean → structures
The area within 50 metres north of the pier also experienced substantial accretion, with shoreline advances ranging from 6 to 77 metres.
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area → experience → metres
Wetland conversion changed the upstream landscape
The researchers also examined land-use changes upstream of the coastline.
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researchers → change → coastline
A wetland area covering about 180 hectares was located approximately 3 kilometres upstream from the Ban Khlong Wan coast and served as part of the catchment supplying sediment to the Khlong Wan Channel.
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area → cover → Channel
Historical aerial photographs and satellite imagery showed that the area was predominantly natural wetland between 1966 and 1976.
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area → show → 1966
By 1995, approximately 100 hectares had been converted into aquaculture farms.
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hectares → convert → farms
The paper describes this as 58% of the wetland area, but that percentage does not correspond mathematically to the 100-hectare and 180-hectare figures reported in the same section.
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percentage → describe → section
To avoid reproducing an internally inconsistent calculation, the figures can be stated without the percentage.
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figures → avoid → percentage
…and 11 more, not listed.
The Aporia
