The Ingleside, Elanora and Warriewood Overland Flow Flood Study catchment area is within the Northern Beaches Council (NBC) local government area (LGA). It includes the suburbs of North Narrabeen, Warriewood, Elanora Heights and part of Ingleside. The catchment is located north of Narrabeen Lagoon and drains to the ocean, with an entrance at Narrabeen Head. The study area covers an area of approximately 1,650 hectares (16.5 km2). In the upper portion of the catchment there are few major overland flow paths with significant concentration of flow, outside of the creek channels. These channels contain most of the catchment runoff even in more severe storms like a 1% Annual Exceedance Probability (AEP) flood event. The southern part of the mid-catchment comprises the residential area of Elanora Heights, draining primarily to Nareen Creek, while the northern part is remnant bushland, draining to Mullet, Fern and Narrabeen Creeks. The catchment experiences widespread shallow overland flow, with relatively few concentrated flow paths apart from the creek channels. The design events investigated include the Probable Maximum Flood (PMF), 0.1%, 0.2%, 0.5%, 1%, 2%, 5%, 10% and 20% AEP flood events. The models and results produced in this study are intended to also form the basis for a subsequent floodplain risk management study where detailed assessment of flood mitigation options and floodplain risk management measures will be undertaken. Therefore, the models established in the flood study need to be suitable for use to assess a range of management options in the floodplain risk management study.