Development of Multi-Attribute UHRUs for Stormwater Management

Marija Eric, James Li and Darko Joksimovic


Urban Hydrological Response Units (UHRUs) are urban drainage areas that contain similar runoff generating mechanisms. Urban drainage areas which comprise an UHRU exhibit similar hydrological characteristics such as slope, lot area, soil type, and % imperviousness. Runoff from this UHRU can be extrapolated to other areas that also share similar hydrological characteristics. LID technology systems can therefore be simulated or modelled at the lot-level and then extrapolated to the larger scale of the watershed-level. This method was used to evaluate the performance of Low Impact Development (LID) technology systems on pre-defined stormwater areas within the Lake Simcoe’s watersheds which were never subjected to conventional stormwater management practices (Li et al., 2010). The main objective of the current study is to further develop a methodology for the hydrological modelling of LID technologies using the UHRU approach. Data pertaining to the hydrological characteristics of all of the urban parcels in the City of Barrie, Ontario, was first compiled into a common database. Next, a small computer program was created in order to simulate the runoff response of the parcels with and without LID implementation using US EPA SWMM software. At present, a cluster analysis is being performed to determine groups of lots with similar hydrological characteristics. At first, all of the lots are used to form different clusters and the centroid of each cluster or a lot which most closely resembles the centroid is determined. These lots will then be used as input data when running the hydrological modelling software. The lots are further divided into different categories and cluster analyses are performed to generate more input data. Various results from the cluster analyses are compared and generate an approach to develop UHRUs.

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