Abstract
Flooding is one of the most weather related safety hazards in California and has caused massive property damage and/or loss, and human casualties. Flooding occurs due to the fact that it is a drainage basin for thousands of acres of foothills and mountain land surrounding the valley. Snowmelt and precipitation would runoff and drain to the central valley before entering the ocean. Due to its diverse natural landscape, low elevation and flat nature, California’s central valley is one of the most flood prone areas in the world. California has developed many systems of flood management facilities including flood control reservoirs, levees, weirs, diversions, etc. However, potential for flood hazards in residential areas remains serious due to uncertainty in weather patterns and developments in floodplains. It is often believed that these systems will protect areas from all flood disaster. Although it is true that these systems provide a level of protection, residual risk of flooding still exists indicating that these systems were designed to reduce the risks of flooding, and not to eliminate the risk completely. Flood forecasting is one of the key flood management practices in the United States. Early flood warming has proven to be critical for better management of the flood risk to reduce flood related life loss and property damages during high water events. Availability of appropriate forecasting tools and procedures that allows timely and accurate flood forecasting helps flood emergency response managers to make necessary decisions for preparedness, response and recovery from significant flood events. The California Department of Water Resources (DWR) and California Nevada River Forecast Center (CNRFC) jointly forecast flood warning stages at 96 locations along the rivers and streams in the state of California. A coupled one dimensional (1-D) and two dimensional (2-D) hydraulic modeling system has been used for this study to focus on the impact of high stages including flood, danger and beyond in the Bear Creek on the residential areas and facilities within the City of Merced, California. This study attempts to improve the understanding of application of a coupled 1-D/2-D Hydrologic Engineering Center River Analysis System (HEC-RAS) numerical model in real time forecasting of flood warning stages in the Bear Creek. This study will also improve the understanding of the impacts of these flood warning stages in terms of inundation extents, timing to support warnings and evacuation priorities, reducing human casualties and minimizing property damages by undertaking steps to recover from flood waters.