Hydraulic Studies for Proposed Oddaimavadi Bridge at Valachchena

The impact of any major restriction on a river has to be considered in the design of bridges due to rapid urbanization of river estuaries. This aspect can not be ignored any longer and therefore it is necessary to verify the hydraulic conditions before and after a new construction. The existing bridge at Oddaimavadi over the Maduru Oya in Batticaloa District needs replacement. Major land use changes had taken place, since the construction of the existing bridge. The specific objective of this study was to determine the minimum span of the bridge to avoid any significant inundation in the upstream and further to keep the deck level of the bridge above a safe level to withstand a major flood of rare probability.

A numerical hydraulic model was set up for the river estuary to simulate the conditions during a design flood of 100 year return period. By simulation the deck level of the bridge was kept sufficiently above the high flood level and the span of the bridge was optimized to minimize the upstream flooding. The HEC-RAS hydraulic model for hydraulic modeling and HEC-HMS model for hydrological modeling developed by the US Army Corps of Engineers were used in this study for simulation