This blog post was written while I was a fellow at the Institute for the Built Environment (IBE) at Colorado State University. The original post can be found here.
Many people consider rivers in urban areas to be dirty, dangerous, and polluted. Unfortunately, they aren’t always wrong. Urban rivers are convenient dumping grounds for waste, and can flood, threatening homes and businesses. However, it doesn’t have to be this way. Urban rivers should be viewed as assets — places for nature, clean water, and recreation — that can enhance our communities.
The typical way we manage rivers increases the risk of flooding
It’s no coincidence that most cities have historically been built along rivers. Rivers provide water for drinking, irrigation, and industry; can be used for transportation; and offer a convenient place to dispose of sewage. As cities have grown, they have continued to restrict and hem in rivers, often turning dynamic natural ecosystems into little more than canals. This damages river function and also puts our cities at increasing risk of harmful floods. As recent, high-profile floods across the US have shown (e.g., Houston in 2017, Colorado in 2013), it’s not a question of if the floods will come, but when.
Flooding is a natural phenomenon and only results in disaster when humans get in the way. As cities continue to grow, we are increasing our own vulnerability. While nature doesn’t distinguish race or wealth, natural disasters disproportionately impact the most vulnerable populations. This is because neighborhoods that are home to poor and marginalized populations are often located on cheaper land next to river corridors. These populations are more at risk from floods and have fewer resources to respond to them. Cities aren’t going to stop growing anytime soon. So, what can we do to reduce our flood risk?
River restoration can reduce flood risk
Floods occur when there is more water than a river channel can hold. The best approach that cities can take to reduce flood risk is to give the river more room. Restoring floodplains along urban riparian corridors provides space for surplus water, and keeps it from inundating homes and businesses. While simple in concept, this is often difficult in practice.
Due to typical patterns of development, most land along urban rivers is privately owned. Cities, therefore, must buy up this land, remove any buildings, and restore it to a more natural state — an expensive prospect for cash-strapped local governments. But considering the cost of flood damages, buying land may be the most cost-effective solution. Still, since floods generally happen only occasionally, how can cities justify letting valuable land sit vacant?
Making these riverside areas into parks and natural areas can provide an important community amenity that won’t be damaged by flooding. For example, the Bishan Park in Singapore has a naturalized stream that offers flood protection while also serving as a popular recreational area. Smaller cities have taken similar approaches; for example, the city of Fort Collins, CO, turned much of the land along Spring Creek into parks and open space to help prevent a repeat of the devastating 1997 flood.
River restoration can improve water quality
Rivers, unfortunately, still receive a lot of our waste. While we now treat sewage before it enters rivers, there is plenty of other pollution that burdens urban streams. Every time it rains, the oil, trash, pesticides, and other waste that coats our streets and yards wash into rivers. Dog waste alone is a major contributor of E. coli and other pollution in urban rivers. All of these problems make most urban rivers unsafe to swim in. Cities are working to reduce these sources of pollution, following the Clean Water Act, with the goal of making rivers fishable and swimmable. Restoring the river ecosystem can also improve water quality. Rivers and their floodplains act as filters — cleaning water before it reaches the stream — making the river a healthier home for fish and other wildlife. Restoring these natural river functions — by creating floodplains, planting trees along the banks, and allowing the river to naturally move and shift — can be a valuable tool for addressing urban water quality issues.
Denver’s National Western Center Redevelopment & the South Platte River
The Institute for the Built Environment (IBE) at Colorado State University is one of many project partners working on the National Western Center Redevelopment project in north Denver. The 250-acre site is being reimagined to connect surrounding neighborhoods to the city and to the South Platte River — reuniting people with this neglected resource. One of IBE’s roles is to assess how project decisions can benefit the river and the community; for example, by estimating how restoring the South Platte’s floodplain could reduce flood risk for surrounding neighborhoods. Through my fellowship with IBE, I’ve used modeling to show that creating even a relatively small floodplain could reduce the extent and depth of flooding for nearby homes and business.
While this is just one small site along the river, there are some clear benefits to floodplain restoration at the National Western Center. Imagine that the river was given more room to flow and shift naturally throughout the city; this could reduce flood risk, improve river health, and give residents more river access — all while making the South Platte a centerpiece greenway for Denver.
Restoring urban rivers won’t fix all of the flooding and water quality problems that cities face. But it can be an important part of the solution, bringing back these amazing ecosystems for the animals — and people — who depend on them.