Effectiveness of Ubol Ratana and Lam Pao Reservoirs for Flood Mitigation in the Downstream Area of the Chi River Basin using HEC-HMS model

摘要

The Chi River Basin is vulnerable to flooding due to its location in the pathway of tropical storms during the monsoon season, flat topography, large proportion area of community settlements and agricultural activities and poor management of water release from dams. Since there is still a lack of lasting viable solution to flooding problems, an insight into detailed aspects of flood alleviation needs to be addressed. The objective of this study was to perform rainfall-runoff analysis using Hydrologic Modelling System (HEC-HMS) model in order to assess the effectiveness of Ubol Ratana and Lam Pao reservoirs for flood mitigation in the downstream area of the Chi River Basin. A scenario-based study that investigates the attenuation of flood peak discharge downstream of the Chi River Basin for the year 2001 was presented. Water storing and releasing scenarios from different reservoirs were designed to cover possible situations. The HEC-HMS model was used to simulate the attenuation effect of downstream flood hydrograph. The simulated results showed that the decrease of releasing water from Ubol Ratana and Lam Pao reservoirs by 10, 30 and 50% during the wet year (2001), affected the decrease of peak flood by 5.86%, 17.57%, and 26.59%, respectively. In conclusion, reducing existing reservoir releases should be considered as part of proactive flood risk reduction measures, and the HEC–HMS model is able to describe the hydrological processes through underlying physical and mathematical relations.