ANALYSIS OF RUNOFF-REDUCING MEASURES USING A DUAL DRAINAGE HYDROLOGIC AND HYDRAULIC MODEL IN AN URBAN CATCHMENT IN THE METROPOLITAN AREA OF CHICAGO (IL)

Green Infrastructure (GI) is commonly used to reduce runoff in general in urban areas. However, there is a lack of methodologies to assess its effectiveness. Herein, three types of green infrastructure (GI): rain barrels, green roofs and pervious pavements are implemented in a Dual Drainage Model (DDM) for a catchment in the Metropolitan Area of Chicago (IL); with an extension of approximately 31 Km2 and using the 100-year return period and 3-hr design storm. The three GI are applied in an equal proportion to existing impermeable areas of the blocks (5%, each). The results show that rain barrels have little influence in runoff reduction (less than 0.5%) while pervious pavements produce a reduction in runoff of 7.47% while green roofs result in a 5.66% reduction. When all GI are implemented a reduction of 13.44%is achieved almost as high as with green roofs plus pervious pavements. The reductions in number of streets affected by a hazard criterion based on water depths (greater than 0.3m) is only 27 (Total number of streets: 7104) using rain barrels, 134 for green roofs and 149 for pervious pavements. Using both green roofs and pavements the reduction is 245, similar to using all GI simultaneously.