A setting-back of coastal dike to protect the wetland was carried out in 2004 near the mouth of the Maite River flowing into the Nakatsu tidal flat. Monitoring surveys, such as beach surveys and investigations in coastal vegetations, had been carried out between 2005 and 2009 after the setting-back.During the observation period, Typhoon No. 5 attacked the coast on the 2nd of August in 2007, resulting in the increase in tide level up to DL+4.7 m, which is a maximum since 2000. Due to the storm surge,shoreward sand transport occurred and a high berm with a height of 5.02 m was formed with the recession of the foreshore by 5 m. No changes were observed in the wetland and its environment was maintained despite the storm surges, suggesting that the setting-back is useful for protecting the wetland against storm surge.
Long-term changes in sand bar in Sanbyakken region in Nakatsu tidal flat were investigated through the comparison of the aerial photographs. Great changes have occurred in this sand bar in recent years, as aresult of increase in eastward longshore sand transport since 1998. The reason was studied in terms of change in wave field. Waves with the direction of N70deg E, which was determined from the shape of the sand bars on the tidal flat, were significantly sheltered due to the offshore breakwater of Nakatsu Port. Takingthe refraction effect of these diffracted waves into account, the tip of the sand bar was also sheltered by the waves. It was found that this caused increase in longshore sand transport.
This paper combines primary and secondary data to highlight the sociocultural values and ongoing change in a coastal mudflat ecosystem in Nakatsu, Japan. We carried out focus group discussions (FGDs) with key local stakeholders including both local community whose livelihoods depend on the traditional and local knowledge (TLK) based use of the mudflat as well as local experts, providing a transdisciplinary knowledge platform. We identified 1 2 ecosystem services that are related to the wellbeing of the local community. While provisioning of food is a key ecosystem service identified by the respondents, some of the cultural services related to the aesthetic beauty, and mental satisfaction and hope, education and knowledge on the mudflat as well as supporting services related to the mudflat as a coastal life support system hold high importance . These are the values that pivotal for the conservation of the mudflat. R espondents indicated that several key provisioning , cultural and supporting ecosystem services have degraded over time through habitat change and loss, and overexploitation. Underlying drivers of change of these ecosystem services include ageing, depopulation, economic diversification, and technological change that has eroded TLK practices associated with sustainable use of the mudflat . T he paper shows that knowledge on ecosystem services and their degradation through a transdisciplinary knowledge platform provides useful information on how a mudflat gets degraded and this is not understandable from the change in the areal extent of the mudflat only.
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