Drywells and trees: combating urbanisation-induced flood, heat and salinity programs (GC22009)

What is it all about?

This project will generate quantitative evidence of an adapted water- and climate-sensitive urban design feature for residential gardens – and the role that trees play in enhancing the effectiveness of drywells in water management. The design pairs a drywell and a tree(s) and connects the garden and roof to restore urbanisation-induced hydrological alternations and combat flood and extreme heat problems in cities.

Challenge

Private properties in cities have a huge potential to restore urban hydrological processes, if impermeable roof catchments and permeable gardens are hydrologically connected in an efficient way. It is estimated that roof catchments of private dwellings have a rainwater harvesting capacity of 43.8 GL per year in metropolitan Adelaide. Less than four per cent of this capacity is currently used. One limitation to increasing rainwater harvesting is that many houses (particularly those of new and infill developments) do not have space to install rainwater tanks of sufficient storage.

Response

The aim of this project is to unlock the large rainwater harvesting potential embedded in private dwellings in metropolitan Adelaide. The project team will develop and test a prototype of a Water Sensitive Urban Design (WSUD) structure that uses residential roof catchments and gardens to harvest and retain rainwater. This green engineering feature is a drywell paired with a tree(s) and connected with roof catchment (with or without a rainwater tank). A drywell (alternatively called leaky well) is a subsurface void gap-filled with gravels hanging above the groundwater table. The project team will pair it with a tree(s) to optimise its efficiency for stormwater harvesting. In the meantime, the companion trees will grow better to provide more shade, and larger transpiration cooling in summers. 

Benefit

The project will provide an applicable green infrastructure prototype and quantitative evidence to support urban policy changes towards a climate-resilient city. It will directly contribute to industry’s goals of achieving continued growth in urban greening, and urban environments which are prepared for and resilient to floods and extreme heat.