Urban sprawl emerges as main threat to US rivers
Urban sprawl is as one of the most significant threats facing US rivers, according to American Rivers' 14th annual report, America's Most Endangered Rivers of 1999.
The national river conservation organization’s report demonstrates the role urban development plays in the degradation of US rivers, examines and ranks rivers that this year face the most serious and immediate degradation and provides an overview of the current state of US rivers.
One of the most serious problems this year is occurring on the lower Snake River in Washington State, named the most endangered river in America. Over a million salmon and steelhead once migrated up the Snake every year. Today, the river’s salmon runs are close to extinction because four dams on the lower river have destroyed its natural flow, the report says.
“Few people understand the devastating impacts of unplanned, rapid growth on rivers or the hardships that communities face from a wholesale degradation of rivers across the country. We have made great progress in cleaning up our rivers in the 25 years since the Clean Water Act, but sprawl is threatening to reverse those gains,” said Rebecca Wodder, President of American Rivers.
Urban development chews up riverbanks, wetlands and floodplains, destroying wildlife habitat, preventing the filtration of sediment and toxins, and the absorption of floodwaters. Paving over the creates “impervious cover”, the report says, and increases the amount of polluted runoff flowing into rivers and streams. Impervious cover causes more frequent and severe flooding and leads to streambank erosion and habitat loss.
According to the Center for Watershed Protection, when 10% of a watershed is sealed under such cover, the rivers and streams that receive its runoff will be degraded. And when 25-40% of a watershed is paved over, its rivers and streams can often no longer support fish and wildlife and are not safe for human uses.
In the Seattle area, the report says, development is sucking water from the Cedar River, while runoff is polluting the water that remains – destroying the river’s salmon and steelhead runs. The growth of Chicago is overloading suburban sewage treatment systems, forcing regular discharges into the Fox River to get rid of the excess.
Sprawl also increases demand for water. Urban areas are pumping water directly from nearby rivers – or from area aquifers that feed rivers – at alarming rates and with devastating impacts for fish and wildlife, the report says.
The suburbs of Atlanta are diverting more and more water from the Coosa and Tallapoosa headwaters which feed an Alabama river basin, one of the richest sources of freshwater aquatic animals in the world. Sierra Vista, Arizona is depleting groundwater so quickly that flows in the San Pedro River, one of the country’s most important migratory bird flyways, are down by 30%. Salt Lake City’s water consumption is reducing flows in the Bear River and threatening one of the world’s most remarkable bird refuges.
American Rivers called on local and state governments to reduce the damage sprawl causes to rivers. The organisation urged governments to limit the spread of impervious cover and to encourage re-development of high-density areas by restoring urban riverfronts.
State and federal agencies should protect and restore rivers that are impaired by excessive water withdrawals, the organisation said, by encouraging water conservation through water pricing, as well as through existing laws such as the Clean Water Act, the Endangered Species Act, and state water laws.
“The rivers flowing across our country are precious beyond words. Few people realize that the United States supports the greatest diversity of freshwater animal species in the world. But at the same time, freshwater animals are the most threatened group of species in the country. The loss of these species is a warning to us. If sprawl continues to ravage rivers, we will lose not only wildlife but also our drinking water supplies and economic and recreational opportunities,” warned Wodder.
The report also shows that while sprawl puts rivers at risk all over the US, many other threats continue to damage waterways, including mining waste, dams and riverbank manipulation.