Change Detection in Coastal Zone by Remote Sensing Technique
Mrs. Valairat Wanpiyarat, Ms.Promchit Trakuldist, Mr. Boonrak Pattanakanok
Land Development Department,
Ministry of Agriculture and Cooperatives, Thailand.
Abstract
Because land use information was limited, therefore, the Landsat TM color composites, band 432 (ROB) acquired on May 29,1989, and band 453 (ROB) acquired on September 24,1991, and September 10, 1992, were visually interpreted for land use changes detection in to the coastal area of 340 km 2 at Amphoe Pak Panang, Nakhon Sri Thammarat province. The results of interpretation and field verification revealed that the increasing of shrimp fans , during 2 the past three years, was up to 25.78 km due to the encroachment of mangrove forest and land use change from paddy land to shrimp fanning. Dispersed salt water, generated from shrimp fans, created soil salinity and water contamination to the nearby paddy fields, resulted in paddy abandonment. The total abandoned paddy field was found to be 17.80 kIn The coconut and banana area increased about 9.84 kIn2. Approximately 13.63 kIn2 of the mangrove forest was destroyed and the highest depletion area, 9.72 kIn 2 ,was found between the year 1991 and 1992.
In addition, the Landsat TM images also showed that the coastal shore lines had been changed from year to year indicating the usefulness of satellite image for update mapping.
I. Introduction
The history of development of the Pak Phanang River Basin has long been more than 10 years. The first real developmeilt concept was created in 1980, with consideration of the Large-
Scale Project Section, the Project Planning Division, Royal Irrigation Development. Up to now the serious problems in the Pak Phanang River Basin can be described as
-
Shortage of fresh water for irrigation development and for domestic uses,
- Salt water intrusion into the Pak Phanang River and tributaries which lasts about 9 months each "year, causing shortages of fresh water into the lower Pak Phanang basin,
- Conflicts of interest between rice farmers and marine shrimp farmers due to discharges of salt water from shrimp ponds into paddy fields, causing damages of rice fields along the coastline of the Gulf of Thailand, along the Pak Phanang River, and along the Khlong Cha Uad,
- Annual flooding problems which usually occur in the period from November and December reach year causing damages of houses, infrastructure, and agricultural areas of more than 1 ,248 km
These serious problems have to be mitigated, and this is the reason why it is necessary to
develop Pak Phanang River Basin.. His Majesty the King, during his visits to Southern Thailand m 1992, gave the Royal Irrigation Deportment his concept of building salt water barrage tat Ban Bung Pi, Tambon Hulong, Amphoe Pak Phanang, Nakhon Sri Thammarat province as well
as a series of drainage canals in order to solve the above -mentioned problems
In order to mitigate the conflicts between the rice farmers and the shrimp farmers in the area, land use zoning delineation between fresh water and saline water zone is very necessary Therefore, the Department of Land Development. has carried out land use surveying, emphasizing on land use changes in the paddy area and the mangrove forest. Those existing land uses including the distribution of shrimp farms are basically required for creation of reasonable dividing line.
2. Study Area and Objective
The study area is located between 8 ° 15 to 8 30 N latitudes and 100 05 to 100 17' E longitudes covering about 340 km2 in the Pak Phanang River Basin , eastern side of Nakhon Sri Thammarat province of the southern peninsula Thailand. Its physiography composes of bays,Li sandy beaches, river mouth, dunes, and tidal flat. The north side of the study area in the river mouth of the Pak Phanang River, is covered with mangrove forest while the rest mostly contains agricultural land ( Figure 1 ).
a. May 29, 1989. Band 432
b. September 24, 1991. Band 453
c. September 10, 1992. Band 453
Figure 1. Landsat images of the study area, acquiring on May 29, 1989, September 24, 1991, and September 10, 1992 respectively.
Remote Sensing technology provides multiple, repetitive, and update physical information. For this research, the authors aim to apply remote sensing technology to monitor land cover and land use changes especially from mangrove forest and or paddy to shrimp farm, and also estimate shrimp fanning area in the study area.
3. Methodology
The methodology includes an analysis of temporal Landsat TM images, field verification, polygon overlay, and monitoring of land use changes.
An amount of three Landsat TM images, acquired on MultiMate between the year 1989 and 1992 and produced at scale 1 : 50,000 was visually interpreted for land cover / land use investigation. The qualitative comparison of land use changes work during d1e period of d1ese data.
To observe the circumstances, field verification was carried out in May 1992 and September 1993. In the field, land cover land use, forest condition, soil and water condition were described and recorded.
To study land cover land use changes, the multiple layers of previous interpretation maps were overlaid to create new polygons showing those changing areas. A number of changed polygons were examined and calculated for reporting.
