Overview

In order to properly plan and manage both existing and future development within the floodplain, there is a need for Council to establish appropriate flood planning levels using a rigorous, up to date technical analysis. Webb, McKeown & Associates were engaged by Wellington Council to prepare this Flood Study to provide the technical foundation for the determination of flood planning levels within the township of Geurie (refer to Figure 1). The primary objectives of the study are:

• to define the flood behaviour for the Boori, Geurie, Heatherbrae and Limestone Creek catchments within the Village and Rural 1(c) areas,
• to establish numerical hydrologic and hydraulic models to determine flood flows, velocities and levels for various design events,
• to formulate the models such that the effects on flood behaviour due to catchment development and possible flood mitigation measures can be investigated in the future.

This report details the methodology used and the results of the design flood analysis. It includes:

• a summary of available data,
• reasons supporting the choice of hydrologic and hydraulic models,
• establishment of these models,
• definition of design flood behaviour in accordance with the NSW Floodplain Development Manual (2005).

All levels provided in this report are in metres (m) to Australian Height Datum (AHD) which is the standard national survey reference plane approximating mean sea level. A glossary of flood related terms is provided in Appendix A.

Results for Geurie Creek, Boori Creek, Limestone and Heatherbrae Creeks, Overland Flooding and Rural Small Holdings north of the village, are discussed