Runoff Change Study Using Remote Sensing and GIS in Southern Taiwan

Abstract

Taiwan has been experiencing fast economic development and population growth for thepast twenty years. This development has put pressure on the agriculture and overall hydrology ofthe nation. To cite but few, peak runoff increases significantly in the urbanized area due to theincrease of runoff coefficient which was caused by the over-development of neighboring farmland,the construction of new houses, roads, factories, nursery and plastic-mulched farms. Furthermore,the drainage system has not been upgraded accordingly and, as a result, poor drainage and severefloods have occurred. A study employing remote sensing for obtaining periodic regional updates ofrunoff model parameters through land cover analysis, together with geographic information system(GIS) for handling and performing the image processing and runoff curve number estimation, wasperformed in two, one static (Mei-Nong) and the other developing (Niao-Song) basins in Kaohsiung,southern Taiwan. Landsat 30-m resolution imagery from 1990, 1995, and 2000 was processed toland-cover maps. Ground truth data was collected from field survey and historical aerial photos. GISanalysis of this land-cover, together with soil map data, was used to estimate spatially-distributedUnited States Department of Agriculture, Natural Resources Conservation Service-Curve Number(USDA-NRCS-CN) on a 30-m grid, and to compute runoff depths. Results of the study indicate that,integrating remote sensing and GIS for tracking the land cover change hence runoff response washelpful for understanding the trends and possible impacts of the dynamics of the change in land useon the overall hydrology of the two study areas. Niao-Song basin has experienced changes in land cover hence runoff response more than the Mei-Nong basin. Over the 10 years of study, the runoffdepth has changed much attributed to an increase in residential areas and reduced agriculturalareas. The results of the study will be useful in planning, managing and anticipating the potentialchange in the runoff response of the irrigation areas as a result of possible changes in land use.