Hydrological impacts of land use/land cover change in a large river basin in central-northern Thailand

The purpose of this study is to determine the hydrological impacts of land use/land cover (LULC) change in the Yom watershed in central-northern Thailand over a 15-year period using an integration of remote sensing, Geographic Information System, statistical methods, and hydrological modelling. The LULC changes showed an expansion of urban areas by 132% (from 210 km² in 1990 to 488 km² in 2006). The Yom River's daily discharge long-term trend significantly increased at most of the measurement stations (p value < 0.05), and the rate of increase in discharge at areas downstream of the rapid urbanisation was significantly greater than that at areas upstream. There were no significant long-term trends in precipitation characteristics in the basin, except for one station. The rate of change in discharge after changes in LULC showed a systematic increase over a range from 0.0039 to 0.0180 m³ s^-1 day^-1 over a 15-year period, with the increase in urbanised area spanning a range from 81 to 149% in two flood-prone provinces. A rainfall-runoff model simulated a small increase (-10%) in peak flows. The coupling of surface observations, remote sensing, and rainfall-runoff modeling demonstrated the impacts of changes in LULC on peak river discharge, hence flooding behaviour, of a major river in central-northern Thailand.