Author(s): W. Schluter
Keywords: No Keywords
Abstract: The lands of the proposed development are located adjacent to the Sluice River and upstream of the Mayne Estuary, which is a registered special protection area (SPA) and downstream of protected marshlands. The flood assessment in this area is complex as it involves hydrodynamic modelling of the river flows as well as tidal levels. The main aim was to satisfy the planning authority and confirm that the proposed development will not adversely impact upon existing flood levels. The main objectives of this assessment were to develop a hydrological model of the Sluice River catchment to calibrate to historical flow data; Generate design flow hydrograph to enable a joint probability analysis and establish existing flood levels and extent for a range of return periods and critical duration; Determine minimum floor levels, taking into account appropriate freeboard and climate change scenarios, and develop a mitigation strategy, if required. Modelling results showed that the Sluice River upstream of the site and railway crossing has a maximum hydraulic capacity, which is due to its size and bed slope. Independent of any future development in the catchment this would limit the inflow to the site. Findings also show that the low lying areas in the northern section of the site are liable to flooding for all of the events. This is due to the ground elevation, which ranges from 1. 0m to 2. 0m and the gaps in the earth embankment allowing flow to enter this area. The joint probability analysis showed a maximum flood level of 2. 7mOD, using the worst case development condition and a return period of 500 years. A 200 year event would result in a maximum flood level of 2. 5mOD for the same scenario.