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Flood study

Ingleside, Elanora and Warriewood Overland Flow Flood Study (2019)

The Ingleside, Elanora and Warriewood Overland Flow Flood Study catchment area 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).

The major components of the study are: the collection and collation of existing information and additional survey data; the preparation of a hydrologic and hydraulic models; the interpretation and presentation of model results to describe and categorise flood behaviour and hazard for a range of design storm events for the existing catchment conditions, including road flood affectation information for the SES; analysis of hot-spots; flood control lot mapping and ground truthing; undertaking sensitivity analysis; properties at risk analysis; risk to life analysis; and investigating and determining the Flood Planning Area.

Flooding in this catchment can occur together with or independently from flooding of Narrabeen Lagoon. The results produced herein are for Ingleside, Elanora and Warriewood local overland flow events only. Peak flood levels from Narrabeen Lagoon have been modelled and documented in the Narrabeen Flood Study (Cardno, 2013). The levels produced in that study incorporate consideration of both Narrabeen Lagoon catchment runoff and coincident ocean tailwater conditions.

The flood levels to be used for planning at a given location are typically the higher of the levels from each of the studies. Generally in the lower catchment, Narrabeen Lagoon flooding dominates (i.e. the 1% AEP lagoon level produces higher peak flood levels than the 1% AEP local overland flow storm event, and is the critical scenario). There are some parts of the study area where both flood mechanisms are relevant for floodplain management decision-making, and the results from both studies will require consideration.

Additional Information

Field Value
Title Ingleside, Elanora and Warriewood Overland Flow Flood Study (2019)
Publication Date 13 June 2019
Themes Land and Resource Management
Spatial Extent
Map data © OpenStreetMap contributors
Council/LGA Northern Beaches Council
Author/ Prepared by WMAwater
Publish date 22 February 2021
Update date 25 February 2021
River Basin 213 - Georges
Approval State Approved
Submitted for approval 25 February 2021
Submitted by Valerie Tulk
Approved 25 February 2021
Approved by dstazic
Identifier 6fd687f7-5073-4f84-b660-ed6e75182292