Catchment Scale Evaluation of Rear Yard Soakaways and Soil Amendments

Stormwater infiltration technologies such as backyard soakaways and soil ammendments have the potential to reduce the receiving water impacts of development by helping to restore natural infiltration and evaporation functions to the urban landscape.  This project evaluates the hydrologic benefits of these practices by comparing three similar sized residential catchments.  The three catchments are roughly 2.8 hectares each; one has been constructed with rear lot soakaways, another with 30 cm of top soil on each lot and 120 cm of topsoil along the rear lot line, and the third as a control with standard residential development (10 cm of top soil on each lot and no rear lot soakaways). 

Runoff volumes will be monitored on each of the sites, and later adjusted on a unit area basis to account for slight differences in imperviousness, land cover and drainage area size among catchments.  Any differences in the adjusted unit rates will be attributed to infiltration.  The rainfall, runoff and infiltration volumes will be compared on a seasonal and event basis.  Soil moisture and permeability measurements on the control and soil amended sites will also be compared to quantify potential water conservation benefits of the practice.  The results will be used to develop recommendations on how these practices should be best applied to meet stormwater management objectives on new and re-development sites.   

Photo credit: Karl Schneider