The McCarrs Creek, Bayview and Mona Vale Flood Study covers flood prone land in the suburbs of Mona Vale, Bayview, Church Point and Ingleside. It investigates mainstream and overland flow flooding, taking into account backwater flooding from tidal influences in the Pittwater estuary and Pacific Ocean.

Mona Vale, Bayview and Church Point are relatively low lying, urbanised centres in close proximity to the Pittwater estuary. All have heavily modified drainage networks. Ingleside is a steep, rural suburb with some residential development. Importantly it includes the Ingleside Land Release Area, where significant future development is planned.

This report details the results and findings of the Flood Study investigations. The key elements include: a description of the study area; a summary of available historical flood related data; establishment and calibration of the hydrologic and hydraulic models; the estimation of design flood behaviour for existing catchment conditions; sensitivity analysis of the model results to variation of input parameters; potential implications of climate change projections; and identification of the level of flood risk for individual properties in the catchment.

The hydrologic modelling was undertaken using a combination of the XP-RAFTS hydrological modelling software for some catchments and a direct rainfall approach within the hydraulic models for the majority of catchments. Hydraulic models were developed for all sub-catchments using a 1D/2D approach in the ESTRY/TUFLOW modelling suite. These models were calibrated to the April 1998 Event and verified against the October 1987 and January 1989 events. The design rainfall events modelled were the 20%, 10%, 5%, 2%, 1%, 0.5% and 0.2% AEP events and the Probable Maximum Precipitation (PMP).