Case study

Kilgariff Flood and Stormwater Management Plan

ProjectKilgariff Flood and Stormwater Management Plan
ClientNorthern Territory Department of Lands and Planning
LocationAlice Springs, Northern Territory
Disciplines/ServiceStormwater quantity management
Hydrological and hydraulic modelling
Drainage design
Key team members

Greg Roads
Project Manager

Rhys Cullen
Flood Modeller

WRM ContactGreg Roads

The Challenge

The Kilgariff estate, located about 9 km to the south of Alice Springs, was developed to provide a diverse range of housing products and future amenities such as schools, shops and recreational facilities for Alice Springs. The land is to be released in stages depending upon local demand.

The site is affected by regional flooding from the Todd River as well as local catchment flooding from St Marys Creek. Flooding across the site from both of these sources are shallow due to the flat topography and drainage is poor due to the lack of defined drainage paths.

The key challenge was to define a drainage strategy that was sympathetic to the local environment but maximised the developable areas with sufficient immunity from the various flooding sources. The management of stormwater across the developable areas posed a key challenge given the very low relief and ill-defined drainage lines.

Approach and Key Activities

WRM had previously developed hydrological and hydraulic models of the Todd River to define design flood levels throughout Alice Springs and the Kilgariff (Alice Farms) area. These models, which were calibrated to a number or historical events, were refined to include the St Marys Creek catchment and key drainage features of the development site, including the flood storage impacts of Ilparpa Swamp.

The refined models were used to define the extent and depth of flooding as well define the key drainage lines and flood storage areas under pre-development conditions from both flooding sources. Three locations of shallow flood storage area were identified as potentially suitable for future development. In conjunction with urban planners, a provisional development layout was designed that satisfied the expected future residential and commercial demand. The models were used to locate and design flood mitigation measures to provide suitable flood immunity for the developable areas as well as assess the impact of the measures on the residual drainage lines. Stormwater measures were also developed to mitigate the impact of the development on downstream flows.

Outcomes and benefits

The flood modelling and mapping enabled the identification of suitable developable land on the floodplain to satisfy the growing population of Alice Springs. The models were also used to develop a drainage strategy that was sympathetic with the natural environment and provided sufficient flood immunity to the future community.