to rebuild and repair their infrastructure, one resource they are beginning to turn to is the rivers and creeks that flow through urban areas. As we discussed in part 1, cities large and small are spending money, time and effort to restore their waterways. One of the earliest stream restoration projects was in Kalamazoo, Michigan. Beginning in 1986, a 1/3-mile stretch of the Arcadia Creek was uncovered and “daylighted” to help the city address storm water runoff problems and reinvigorate a downtown business district, at a cost of $18 million.
In San Luis Obispo, Cal., a much less expensive project (the total investment was $100,000, but a great deal of in-kind donations of labor and materials were made by local business owners) defeated a proposal to cover the downtown creek that shares the city’s name. Paul Hoobyar, of the National Park Service, describes these efforts in the excellent report “Daylighting and Restoring Streams in Rural Community City Centers: Case Studies“:
The community eventually gained consensus on a design for the creek’s restoration. The agreed-upon design called for widening the creek’s floodplain and re-contouring the streambanks. The design also incorporated building terraced stone walls to prevent bank scouring during high winter flows. The City Council adopted the restoration design, as well as a flood management policy that was atypical for cities at that time. The city policy avoided creating the usual concrete-lined, trapezoidal channels that many communities were adopting for flood control…. the City began developing a program designed to protect the creek while reducing the risk of flooding.
As climate change and associated severe weather events are becoming issues that city leaders have to tackle, three major cities are working on different restoration projects.
In Boston, the Muddy River Restoration Project is a massive, multi-pronged, multi-year initiative for a 3.5-mile section of the river to improve flood control and water quality, enhance the aquatic/riparian habitat, rehabilitate the landscape and historic resources, and implement Best Management Practices. Among the many goals of the project are the reduction of sedimentation from local sources and the use of underground particle separators to remove sediment, as well as the removal of invasive plants and their replacement with “a diverse cross section of plantings including emergents, wetland species, low and high shrubs and trees.”
In Austin, as discussed in Part 1, the Waller Creek Conservancy is partnering with the city to restore the 1.5-mile creek that runs from the north end of the University of Texas campus into the Lady Bird Lake (a dammed section of the Colorado River). The Conservancy recently ran an international design competition, eventually selecting the Brooklyn, NY-based firm Michael van Valkenburgh Associates to develop a master plan to restore the degraded creek and connect three parks along the Creek into a riparian greenway. The city is also just completing a massive project to capture storm water runoff in an adjacent pipe to help avert some of the disastrous flooding that can come from sudden and torrential downpours. (Two days after I left Austin, which was bone dry at the time, 13 inches of rain fell there in just a few hours, flooding many portions of the city.) Waller Creek, along with its neighbors Shoal Creek and Barton Creek, must also play roles in natural flood prevention, and they need to be able to sustain both drought and sudden, intense storms.
The third major project is in Atlanta, where the little-known Proctor Creek runs from near the Georgia Tech campus into the Chattahoochee River. Though diminutive, the stream is responsible for 42 percent of the pollutants that flow into the Chattahoochee from Atlanta. The Proctor Creek Watershed was recently named one of 11 newly selected Urban Waters Federal Partnership locations, with five “champion” federal agencies and five additional federal agencies working to help the state and city improve many overlapping environmental and public health issues, including illegal dumping, brownfields, blighted sites, impaired water quality, pervasive flooding, and combined sewer overflows. The Trust for Public Land is one of the non-profit partners in this effort, supporting the creation of a mitigation bank. Private sector partners will restore the banks of the creek, remove invasive species and contaminants, and restore the natural hydrologic functions, while also creating a 7-mile accessible greenway trail along the water.
With so many communities investing so much time, energy and money in urban stream restoration, what are the expected outcomes? The field is still relatively young, and a thorough study by Kenneth B. Brown of the Center for Watershed Protection (evaluating 24 different types of restoration practices and including 450 individual practice installations) yielded optimistic as well as less positive conclusions. On the plus side, according to the study “overall, nearly 90% of the individual stream restoration practices assessed remained intact after an average of four years.” On the other hand, habitat restoration was not as successful, with the study finding that “less than 60% of the practices fully achieved even limited objectives for habitat enhancement.”
Overall, it appears that cities should proceed with these ambitious plans, but we would all benefit from a much more widespread and detailed sharing of the best (and least) successful models, helping our cities to retain an是梧桐客栈开辟的门户社区