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City of Portland, Oregon
Portland is a leader in urban stormwater management. With over 700 bioretention (rain garden) systems throughout the City, low-impact stormwater design is well integrated into most new and major rehab construction. The general types of systems used fall into 3 categories:
Curb-Cut - Existing curbline is maintained, with linear rain garden installed behind the curb. Curb is cut (and modified to better intercept flow) to allow stormwater to enter. Excess stormwater exit over a wier or is allowed to back up and continue flowing to conventional stormwater collection system.
Bump-Out - Existing curbline is moved into the street and a linear rain garden is installed in area that was previously parking or travelway. Flow through these systems is similar to the Curb-cut systems. These systems are useful as traffic calming systems, or for areas that lack adequate space behind the curb.
Large Scale Rain Gardens - Where space allows, large scale rain gardens can handle a significant amount of runoff from surrounding impervious areas. These are often installed in conjuction with other LID practices.
The City of Portland website has construction details and specifications for the design and installation of these various systems. Photographs of each type of stormwater management system are provided below. along with some creative and artistic approaches to dealing with stormwater.
Much of the original design work for the curb-cut and bump-out rain garden retrofits in Portland was done by Kevin Robert Perry, an award winning landscape architect with Nvue Ngan Associates.