Chapman and Greenough River Flood Project

The Mid West Gascoyne District Emergency Management Committee and City of Greater Geraldton both have an identified role in State Hazard Plan - Flood, particularly in the prevention/mitigation, preparedness and response phases.

Severe floods do not happen often, so the extent of flooding and its consequences, including the loss of life and damage to property, are usually forgotten with time. For the Chapman River and Greenough River area, there requires significant research and community engagement.

The City received grant funding from the State Emergency Management Committee through the National Disaster Resilient Program to develop the flood mapping and modelling.

Project Summary

The project is a flood risk damage assessment study of flood affected buildings and infrastructure in the surrounding the Chapman River and Greenough River catchment areas.

Aim

The project will:

  • create floodplain mapping for the full range of possible flooding events (up to the Probable Maximum Flood (PMF)) to understand the communities potential exposure to river flooding.
  • create a comprehensive flood intelligence database of flood affected buildings (i.e., residential, commercial, major sheds, public facilities) in the area for 1 in 10, 25, 100 & 500 AEP and PMF flood events, and this will also include a 0.9 metre sea level rise. The ArcGIS database will contain information on individual flood affected buildings including floor levels, flood levels & depths of flooding for varying flood scenarios and expected flood damage costs.
  • map the spatial distribution of flood affected buildings and infrastructure for varying flood scenarios using ArcGIS software.
  • estimate the potential cost of direct tangible damages caused in the varying flood scenarios.

Objective

The project’s objective is for emergency response planners and local governments to gain a better understanding and increased awareness of the risk/impact of major river flooding. Specifically, the project will:

  • identify hot spots of potentially high flood damages through the mapping of flood affected buildings and infrastructure.
  • provide flood intelligence to Department of Fire & Emergency Services (DFES) and local governments in targeting specific areas for priority flood emergency response activities in order to minimise potential flood damages.
  • improve awareness of potential flood impacts to the community, local governments, planners, through the value-adding of flood affected buildings and infrastructure to the existing floodplain mapping.

Floodplains continue to be under pressure from more intensive uses despite the significant flood risk. This pressure is increasing as desirable undeveloped land becomes scarce, especially in urban areas.

Severe floods do not happen often, so the extent of flooding and its consequences, including the loss of life and damage to property, are usually forgotten with time.

Greenough River Flood Maps

The Greenough River flows for 240 km from east to west, commencing north east of Geraldton within the Yilgarn Block, meandering across extensive Midwest farm lands and sand plains of the Perth Basin then through the Dividing Ranges in the east, before discharging at Cape Burney estuary approximately 10 km south of Geraldton. The topography within the Greenough River Catchment is generally relatively flat to undulating, with elevations ranging from approximately 455 m AHD in the Dividing Ranges to the north, sloping down to sea level over a length of approximately 260 km at its outlet.

10 Year Maps

/Profiles/cgg/Assets/ClientData/5174_DepthMap_10y_Map1_A3L.pdf

Chapman River Flood Maps