Degradation and Improvement of Urban River Water Quality

The need to understand urban water quality has become a very important area of research and management in the aquatic sciences. Decades of urban development generating high rates of impervious surface, complex networks of stormwater control mechanisms and declining river water quality has created a demand for greater study. In this chapter, issues such as stream bank erosion, flooding, sediment pollution, bacteria and channelization are presented as drivers of the urban water environment. Methodologies and study designs to document these impacts are discussed. Ideas to improve the urban condition such as retrofitting previous development, infiltration of surface runoff, stream restoration, dredging and rehabilitation of lakes and compartmentalization of future development are explained and detailed as ways of integrating the natural landscape features into improvement of our urban centers. Finally, the incorporation of citizen science into adaptive policy is suggested as a solution to regulatory and esthetic/recreational need for improvement

Influence of a low-head dam on water quality of an urban river system

Dam removal in the United States is becoming a common practice for stream restoration as these structures age, climate driven precipitation patterns change, and ecological uplift becomes desirable. Yet in highly urbanized watersheds, these dams may operate as retention basins removing pollutants and mitigating hydrological change. While elimination may be ecologically and economically advantageous, sediment and pollutant removal processes may be better protective of water quality and damaging flooding. In Central Virginia, we compared a watershed split between an urbanized subwatershed (\u3e20% impervious surface encompassing 37.8% of the total watershed land surface) flowing through a 18 Ha reservoir with a rural subwatershed (\u3c5% impervious encompassing 63.2% of the total watershed land surface) located in the James River and Chesapeake Bay watersheds. This reservoir is scheduled for removal in the near future. Comparisons of data suggest that while portions of the urbanized watershed are degraded, this condition is not reflected at the confluence where water quality more closely resembles the rural and minimally impervious subwatershed. This conclusion was further strengthened from data collected following an unexpected dam overtopping in August 2018 where the reservoir was temporarily drained because of safety concerns. After the draining, water quality reversed with the confluence resembling the urbanized rather than the rural subwatershed. Most significantly, water quality flowing into the James River quickly and significantly shifted from a good to a degraded condition. This case study suggests reservoirs in highly urbanized watersheds may serve as critical water quality improvement structures and removal as part of a stream restoration strategy must be carefully considered

Watershed Development and Sediment Accumulation in a Small Urban Lake

The ever-increasing development of watersheds has raised the importance of assessing and mitigating the environmental impacts on water bodies located within disturbed areas. The removal of natural landcover can increase soil erosion and runoff along creeks and rivers, leading to heavier sediment build-up in ponds and lakes and to reductions in water quality and impoundment capabilities. For this paper, we described the possible impact from urbanization on sedimentation within a small lake. Landcover maps from two different time periods were compared against lake depths to assess relationships between development and sediment buildup. By understanding the mechanisms potentially leading to the ultimate loss of this lake, it is hoped that remediation strategies to reduce future degradation may be developed