The Richmond River is one of New South Wales largest coastal rivers. The upper reaches flow in a general north-south direction from its source on the Queensland New South Wales border in the McPherson Ranges through Casino to its confluence with the Wilsons River at Coraki. The river continues south downstream of Coraki until it meets with Bungawalbyn Creek, which is the second major tributary of the Richmond River. At this point the river winds in an easterly direction to Woodburn. Downstream of Woodburn the river turns to flow in a north easterly direction passing Broadwater, Wardell and finally Ballina before reaching the ocean. There is a natural constriction in the river and floodplain at the township of Broadwater. This constriction acts to hold floodwaters in the extensive floodplain 'basin' between Broadwater, Woodburn and Coraki. This floodplain 'basin' is known as the Mid Richmond.
This study examines and defines the flood behaviour of the Richmond River throughout the Mid Richmond region by considering flooding influences from the confluence of the Richmond River and Deep Creek to downstream of Broadwater, including sections of Wilsons River and Bungawalbyn Creek and the floodplains on both banks. The objectives are:
- Review relevant studies previously carried out.
- Identify the nature and extent of historical floods.
- Develop predictive tools (computer models) which reproduce historical flood behaviour.
- Define best estimates of the 100, 20 and 10 year ARI design floods and for an extreme flood.
- Produce maps showing the likely flood heights, flows and velocities for the design floods.
