ENSO IMPACTS ON COASTAL RESOURCES AND ENVIRONMENT AT BAN DON,SURAT THANI, SOUTHERN THAILAND BY LANDSAT DATA

摘要

The Landsat data in 3 periods: which are during the El Nino years (1993, 1994, 1997 andrn2002); the La Nina years (1988,1998 and 2000); and Normal year (1989, 1996 and 1999), arernclassified for landuse types and by NDVI (Normalised Difference Vegetation Index). We foundrnthat during El Nino years, the rainfall anomalies are minus (less than normal), the airrntemperature anomalies are plus (hotter than normal), Tapi river discharge anomalies are minus,rnand NDVI's are lower than normal (less growing vegetations). During La Nina years, thernrainfall anomalies are plus (higher than normal), the air temperature anomalies are minus (colderrnthan normal), the Tapi river discharge anomalies are plus, and NDVI's are higher than normalrn(much growing vegetations). In 1998, first half of the year was El Nino, and last half of the yearrnwas La Nina. However, we used the data on 27 April 1998, which is in the El Nino period, so itrnreceived the impact of El Nino.rnFor fisheries statistics at Surat Thani during El Ni?o years, the quantity of fish catch andrnthe yields of aquacultures (shrimp and fish) were higher than average. During the La Ni?a yearsrnthe same parameters were lower than average The areas of shrimp ponds have been increasedrnwith the increasing population. The population of Surat Thani has been increased every year.rnDuring the El Ni?o years, the areas of natural and mangroves were decreased, while during the La Ni?arnyears, the areas were increased.rnEl Ni?o caused higher frequency of tropical cyclone. La Ni?a also caused tropical cyclone butrnlesser than El Ni?o linkage. The linkage of ENSO on MSL is not very clear owing to the small quantityrnof data. During La Ni?a years, MSLs show plus and minus anomalies for one of each year. However,rnwe may conclude that El Ni?o causes higher MSL than mean value. El Ni?o caused lower river runoffrnthan normal. La Ni?a caused higher runoff than normal.rnSTUDY AREA Bandon Bay (9.20 0 N and 99.67 0 E) is located in Surat Thani Province, southernrnThailand. The watershed of the bay is 12,220 km 2, of which an important part consists ofrnagricultural lands and aquaculture. The population living within the watershed numbersrnapproximately 830,000 with fisheries, aquaculture and tourism as their main activities. Ban DonrnBay is an inlet of the biggest river on the east coast of the Southern Peninsula, which is the Tapi-Phumduangrnriver to the Gulf of Thailand, which lies to the east of Surat Thani province. Mangrovernforest plays an important role in the economies of Ban Don Bay, particularly as a source of energyrnand food protein. However, population and economic development pressures have beenrnresponsible in part for the conversion mangroves to various land uses in the past years, I.e.,rnagricultural, residential and industrial sites, salt ponds, ports and harbors, and aquaculture.