The projects objective is to design a bridge spanning across the Murrumbidgee River located near Gundagai. Through the use of hydrological data and hydraulic analysis we will determine the required height of the bridge corresponding to a specific frequency of flood.
To design a bridge capable of spanning the Murrumbidgee River and flood plain will require hydrological analysis which takes into account all upstream data that is required for the catchment area of the river that will pass Gundagai. Once the hydrological data has been found we can continue with determining the hydraulic analysis. The hydraulic analysis is used to determine the flow rate at the bridges location, and in the scenario of the Gundagai region we will be using a 1 in 100 year event which is chosen per the Australian Standards.
Throughout the Hydrology segment of CIVL444 there will be 2 different methods used to determine flow rate, these are the Flood Frequency Analysis (FFA) and the Watershed Bounded Network Model (WBNM). The first method relies simply on past history of floods that have occurred in the past, and the second method is a computer program that analysis a flood based on gauge data.
Once the flow rate of the river is determined we can begin hydraulic analysis on the bridge. The cross sectional area of the river and the soffit level are other factors required when working out the hydraulic analysis. The soffit is the under surface of the bridge superstructure, it has to be a required height in relation with the Roads and Traffic Authority (RTA) NSW. In a 100 year event there has to be an allowance of 300mm gap from the top of the water level to the lowest part of the bridge deck. The hydraulic analysis will look at the forces on the bridge piers as a result of debris crashing into them and the forces of the water. The foundations of the piers will also be investigated for local scouring. The bridge will be designed in relation to the Australian Standards and the