The Necessity of Integrating Basin Management in Urban River Restoration
Abstract:A successful multi-objective urban river restoration project must be founded on a comprehensive basin management plan that includes targeted and implementable strategies to improve the river's function, and effectively engages stakeholders in defining and prioritizing those strategies. The typical highly altered nature of urban river basins adds considerable complexity to the design of a sustainable river restoration such that it is not sufficient to focus restoration on the river alone; instead an urban river restoration plan must also consider improvements that need to be made throughout the basin. This paper outlines the comprehensive approach that is required to identify and address the multiple challenges posed by restoring urban rivers, focusing on a highly diverse small urban watershed.
A simple river restoration can be achieved by reconfiguring the river's geomorphology to mimic natural functions and/or restoring the degraded habitat. However, in highly urbanized watersheds, this approach is insufficient. Complex issues such as a significantly altered hydrologic response to precipitation, disconnection from natural floodplains and destruction of riparian buffers by development to the river's edge, engineered structures that divert or restrict water flow in the river bed or block fish migration, cross-connections in unmapped city piping networks, a myriad of possible pollutants from a variety of historic and non-point sources in the watershed, elimination or degradation of wetland habitat and other aquatic life, and widespread occurrence of invasive species are among the many assaults that urbanization poses to river integrity. In response to the gradual changes in the landscape brought about by urbanization, cities' relationships with their rivers evolve from dependency on the river for water supply and economic growth to one of neglect. Eventually, many cities turn their backs to their river corridors as eyesores and problem areas.
A comprehensive basin management plan is needed to balance actions required to improve the health of a river with those that create and foster a renewed public relationship with the river corridor. The integrated basin management plan and infrastructure program for the Rippowam/Mill River in Stamford, Connecticut includes consideration of these diverse issues, and thus, serves as a model for incorporating instream flow needs, stormwater management and flood control, restored river function and habitat, and public amenities in a comprehensive approach.
The City of Stamford has embarked on an ambitious program to revitalize its downtown area through the removal of a low-head dam and its small impoundment, restoring a free flowing river in the river's lower reaches and creation of a premier urban park along the river banks. The Rippowam basin management plan needs to support these revitalization plans and extend the benefits of river restoration to the broader watershed. The work supporting the plan includes watershed characterization and management planning, wastewater and stormwater system master planning, water quality monitoring and analysis, flow and water quality modeling, urban planning, landscape architecture, and stakeholder/public participation.
In the Rippowam/Mill River watershed, development pressure increases as the river flows south to Long Island Sound. The watershed includes forested headwaters that include five reservoirs that contribute to the city's water supply, estate homes with extensive landscaping, traditional suburban tracts interspersed with large commercial development, and a dense city center near the mouth of the river. Throughout the river corridor, evidence can be found of the city's long history with the river, ranging from agriculture, to diversions and impoundments created for recreation, to dams that date to New England's industrial roots. The diversity within the watershed requires a tailored approach for the particular challenges of each segment of the river and its watershed.
A comprehensive basin management plan is needed to provide an integrated approach to managing Stamford's urban water resources. The watershed's composition dictates increased protections to the lesser developed portions of the watershed while reducing imperviousness and infiltrating stormwater in the lower watershed to re-balance the hydrologic response to increase low flows and reduce high flows. This requires a combination of traditional stormwater management approaches including finding and eliminating illicit connections, improved maintenance, and modifications to city ordinances to retrofitting green infrastructure through redevelopment. While most improvements will be focused on the need to reduce hydrologic response to storms, measures will also be aimed at improving water quality by reducing of nitrogen (a contaminant of concern for the restoration of Long Island Sound) and phosphorus (to reduce the extensive periphyton cover). The changes in hydrologic response create opportunities to re-configure channel geomorphology to increase river stability, reduce the armoring of the river banks, and improve habitat through restored wetlands.
One of the management challenges is evaluating the effects of proposed changes to Connecticut's instream flow rules, which would significantly increase minimum river flows. These changes could have both positive and negative effects on water quality, while better supporting habitat and public recreation opportunities.
Stakeholder involvement is key for identifying and designing areas for increased public access, enhanced recreational opportunities and use of the river to promote multiculturalism as a place where all citizens can come together. Proposed changes in the river and its watershed complement opportunities on greening, sustainability, open space, outdoor recreation, and quality of life. Ultimately the goal is to return the river to an urban natural resource — keeping the river beautiful, accessible, and enjoyable – and seeking to ensure that it remains a valuable asset for the entire community.
Document Type: Research Article
Publication date: January 1, 2010
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