Hydrological Safety of Vaturu Dam by Evaluating Spillway Adequacy

Abstract

Probable Maximum Flood is considered as one of the most adopted inflow design floods in assessing the adequacy of dam structure in current practices. It is the largest flood that could conceivably occur at a particular location and frequently estimated from Probable Maximum Precipitation (PMP). This study incorporates hydrological modelling using HEC-HMS to simulate the outflow providing the results used in the catchment procedure of translation of PMP to PMFs for a 24 to 168-hour duration. The adequacy of Vaturu Water Supply Dams (CA= 40 km2) which is located in Fiji will be assessed in the context of extreme meteorological events of the PMP/PMF magnitude. The flood rise during these events should not exceed or overtop the dam crest level. Vaturu dam is a domestic water supply embankment dam built in the 1980s to cater for the water supply needs of the Nadi and Lautoka supply zones. A conventional reservoir routing procedure using the Goodrich method is then carried out for all PMP/PMF durations, i.e., 24 to 168 hours. During this period, flood rise levels were noted to be restricted to the Dam Crest level of +532 m ASL. The results and its analysis validated the safety of the Vaturu Dam and the ability of the dam to discharge the onslaught of PMP/PMF safely.

Keywords

• Rainfall-runoff
• HEC-HMS
• Vaturu Dam
• PMP/PMF routing