Assessment of wetland ecosystem health in Lower Songkhram,Thailand

A study was conducted to assess the ecosystem health of Lower Songkhram wetland in Thailand, using a newly developed wetland ecosystem health index (WEHI) based on analysis of field survey and secondary data of the most dominant physical, environmental and socio-economic factors extracted by principal components analysis (PCA). The most influential physical, environmental and socio-economic factors identified were rainfall and awareness and participation of the local community, which had positive effects, whereas soil electrical conductivity (EC), biochemical oxygen demand (BOD) and urban development had negative effects. Based on the results, 9 of the 40 land units of the study area were in very good or good health, 11 in reasonable health, while 20 were found to be in poor or even very poor condition. These findings will be useful for decision-makers in planning and executing an effective and holistic strategy to prevent further wetland degradation.     

Experimental study on dynamic equilibrium of headland-bay beaches

A dynamic equilibrium bay (DEB) is an embayment with continuous sediment supply and its shoreline planform can remain stable over a long period of time without erosion or accretion. For coastal conservation of sandy headland-bay beaches (HBB), the concept of using a static equilibrium bay (SEB) is well known, but that for DEB has received little attention. Moreover, an empirical equation for the stability of a DEB is not yet available. Experiments on DEB shape that aim to derive new coefficients in the parabolic bay shape equation (PBSE) for DEB are now being conducted in the laboratory. The work commences from an initial artificial HBB in static equilibrium with sediment supply source from the lee of an upcoast headland. A final equilibrium planform is obtained for the condition with a specific wave obliquity and sediment supply rate until no further shoreline change is found. In order to fit the PBSE for a DEB, a new parameter called SSR (sediment supply ratio) that represents the ratio of sediment supply rate from the source and the potential longshore sediment transport rate is introduced to quantify the balance of sediment to the bay. Alternative C coefficients in the PBSE for DEB, which include wave obliquity and the SSR, are then calculated. These new coefficients for DEB can now be used to evaluate the influence of sediment supply from a riverine source on a DEB and to classify its equilibrium status for planning sediment management strategies in coastal conservation.