3848 LAKE STREET URBAN STREAM PROJECT
City of Canning
In collaboration with the Water Corporation, the City of Canning proposed to convert a section of the existing Cockram Street Main Drain into an Urban Stream. The Cockram Street Main Drain is situated between Cecil Street and Lake Street. The site is approximately 200 m long and 17 m wide at its widest point.
The City of Canning commissioned 360 Environmental Pty Ltd to undertake stormwater modelling to determine the site’s pre-development hydrological regime and assist with the validation of post-development designs.
The channel was initially designed to contain and convey discharge from a 3- year Average Recurrence Interval (ARI) storm. It is located in a City of Canning commercial area. Therefore, it must contain the 10- year ARI storm, as per Water Corporations current operating licence requirements.
This study aims to confirm the pre- development hydrology of the site and then validate the landscape designs proposed, to convert the site into an Urban Stream. The modelling’s main objective is to demonstrate that the drain’s post-development design can contain the minor (10% AEP) flows within the channel.
The pre-development environment was modelled to determine the topwater levels and flood extent in the small minor and major rainfall event in the first stage. The upstream inflow hydrographs and downstream water level information were provided by the Water Corporation, which was then added to a 1D hydraulic model to evaluate if the pre-development site was able to retain the minor rainfall event within the channel. The decision was made to remodel the site using a 1D-2D linked hydraulic model, which was able to predict not only topwater levels in a range of rainfall events but also the areas and extents of breakout flows.
The second stage of modelling was conducted to analyse the changes to the small, minor and major storm events’ topwater level to determine if the new design allows the channel to meet the design criteria.