Quantifying Consequences of Land Use and Rainfall Changes on Maximum Flood Peak in the Lower Nam Phong River Basin

Abstract

When the severity of exposure to flood is being addressed, several related concerns have always been raised to draw attention on a growing flood threat. In relation to this, the extraordinary insight into the seriousness of land use and rainfall changes that could greatly exacerbate flood impacts would need to be highlighted. The importance of the aforementioned issue lies in the main objective of quantifying consequences of how changes in land use and rainfall affect the hydrological processes in the lower Nam Phong River Basin. The use of Hydrologic Modeling System (HEC-HMS) simulation model would add robustness and predictability to the overall results. It was apparent from the calibration and validation processes that there are reasonably close agreement between observed and simulated discharges at Ban Nong Hin gauging station (E.22A), with good correlation coefficients (ENS= 0.78, r2= 0.81 and ENS= 0.77, r2= 0.82, respectively). Thereafter, different what-if scenarios were conducted to determine impacts of land use changes in 2001, 2011 and 2057 and extreme rainfall with different return periods of 10-, 50-and 100-years on hydrological responses. A slight increase in peak flows were equal to 4% and 1%, as a consequence of the change from 2001 land use conditions to 2011 and 2057, respectively. Conversely, a large increase in peak discharges was expected to be 13%, 20% and 27% when the 2001 rainfall event was adjusted to the projected changes in rainfall corresponding to 10-, 50-and 100-year return periods, respectively. In brief, insignificant relation between hydrological response and land use changes was obviously found, but it was of particular significance due to changes in rainfall extremes. Taken together, obtained findings can then be used as a baseline for water resources planning, development and management, as well as flood management perspective.