Abstract:
This research aims to apply geoinformatics to study badlands; sedimentary
structure; evolution i.e. sinkholes, cliffs, walls, columns, and, stracts; and development
factors such as land use change and soil erosion rate in upper Huay Yand basin, Sakaeo
Province, Thailand. The data is collected from various sources, namely (1) maps
such as topographic maps and geological maps (1: 50,000), (2) photographs such as
Arial photographs, data from LANDSAT 5, and data from Unmanned Aerials Vehicles
(UAV), (3) laboratory reports from Land Development Department, Department of
Mineral Resources and Meteorological Department, and (4) fieldwork.
The findings reveal as follows:
1. The study of badland morphology is comprised of four aspects :
sub-landform, formation, sedimentary structure, and evolution. Regarding sub-landform,
the badlands scattered around the piedmont and the river terrace on the intermontane
basin. Rainfall and the water way in the branch of the upper Huay Yang basin cause
horizontal and vertical erosion. The sediment features of each sub-landform are
considered in terms of shape, width, length and depth (sinkholes). The data about
width and length of sinkholes, length of soil cliffs and soil walls collected by UAV are
compared with those collected from the fieldwork. It finds errors in UAV photographs by less than 2 percent, 4 percent and 10 percent in length and width of sinkholes, and
length of cliffs and soil walls respectively. Sub-landform styles are varied according to
the formation, structures, and the time course of evolution.
2. The factors influencing badland formation in the upper Huay Yang basin
consist of the geological structure, stratigraphy, topology, sedimentary structure, soil
properties, climate, and land use change. As for the geological structure, the techtonic
process brings about faults, joints, fissures, half-graben, intermountain plateaus and fast
running water passages. Regarding stratigraphy, the badlands in this area are
comprised of Phra Wihan formation and Plu Kradung formation. This influences the
sediment and soil. Concerning the sediment and soil structure, soil and sediment in the
badlands are yellow, red, and brown and the texture is fine and very fine. Moreover, the
badlands have sandy loam sandy loams and clay, which affect the erosion rate. In
terms of climate, the badlands feature tropical savanna (Aw). Consequently, the
badlands are affected by temperature and rainfall. In particular, the temperature causes
physical and chemical erosion whereas the rainfall affects the horizontal and vertical
erosion rates. As for the land use change, the erosion rate of the badlands is hastened
by the land use change. Over the past sixty years, the forest area has been converted
into the area for agricultural purposes and non-forest uses. The forest area has been
reduced from 98.73 percent to 72.42 percent. Meanwhile, the area of the badlands has
been increased from 1.14 percent to 5.63 percent.
3. According to universal soil loss equation, the moderately severe erosion,
whose rate of erosion is 5-15 tons per acre per annum, occurs in this area.
4. The geoinformatic application allows systematic and efficient studies, for UAV
provide photographs with subtle details up to 5-6 centimeters. However, this tool does
not have a suitable sensor range. Consequently, it cannot accurately detect sinkholes.