The Warambie Estate site is located next to the Karratha Town Centre in an area subject to inundation from cyclonic storm surge and overland flooding. Negotiations were required with State and Local Authorities to set building levels mindful of recent studies relating to long term sea level rise. The seaward perimeter of the site required rock wall protection for storm surge events.
The site contained two watercourses which were initially proposed to be diverted into a single open drain dissecting the development. Hydraulic analysis identified that stormwater could be diverted around the site utilising existing open drains which allowed a significantly greater area to be utilised for dwellings.
Due to the high cost of fill material and highly expansive clays in the in-situ ground a thorough geotechnical assessment was undertaken of the site. This resulted in an earthwork concept where existing soils were excavated and used as deep fill which minimised the quantity of imported material and, with appropriate grading of surfaces, ensured the risk of ground movement due to moisture change were within acceptable limits.
The site was expanded to provide an additional Seniors accommodation area with the entry road also functioning as an overland flow path for the major flood event. This road was designed to function both as a vehicular and pedestrian emergency access with flow depths and velocities controlled so as to not cause a hazard.
Internally the drainage design utilised roadways to eliminate the requirement for any piped drainage and associated maintenance requirements. Earthworks design rationalised catchments and flow paths to minimise property flooding risk in major rainfall events
