Last weekend we witnessed incredible devastation and tragic loss of human life in Ellicott City. The full scope of the disaster won’t be assessed for some time. For many residents, just feeling safe again will be challenging.
Ellicott City sprung up in a bucolic countryside surrounded by rivers and streams and is naturally prone to flooding from the Patapsco River and Tiber Creek. Flash flooding from this storm, which dropped about six inches of rain in two hours, was an extreme event but one that may become more common. The US National Climate Assessment in 2014 reported that precipitation has increased by 71 percent in the heaviest rainfall events from 1958 to 2012 in the Northeastern states, which include Maryland. This trend is predicted to continue. These data are sufficient cause for concern in how we plan recovery and think about our future.
Extreme precipitation is the driver of this disaster, but its effects are exacerbated by two related factors: urbanization and the loss of ecosystems and the flood-protection services they provide.
Ellicott City is part of the urban-suburban zone that stretches from Baltimore to the District. The population of the historic town alone tripled in 40 years, going from 21,784 in 1970 to 65,834 in 2010. Supporting the growing suburban population has required major investment in roads and infrastructure. Roads are not designed to simulate flood plains. They neither absorb water nor impede its rapid flow. Paved streets and infrastructure funnel floodwaters into raging torrents, as we saw in shocking videos from Ellicott City.
Natural, green infrastructure or ecosystems have traditionally been humans’ first line of defense against natural disasters, including floods, landslides and coastal storms. These services that nature provides were ignored for decades in urban planning. That has cost us dearly economically and in human suffering. It makes sense to turn to nature for help in protecting our communities and reducing costs.
Just last month, I spent time at the United Nations University working on ways to create standards and guidelines for incorporating ecosystems into engineering approaches to leverage nature for human protection. We are beginning to see these efforts emerge. For instance, in Wisconsin, the Milwaukee area’sGreenseams project is restoring natural flood plains with wetland areas designed to hold 1.3 billion gallons of water, about 1,970 Olympic-size swimming pools. In Minnesota, Ramsey County developed green infrastructures to reduce localized flooding, decreasing runoff volumes by 99 percent and saving half a million dollars over the cost of gray infrastructure. The Netherlands, a low-lying country that faces extreme flooding, recently created a partnership between the government and the private sector to identify and pursue nature-based solutions that work with engineering approaches to reduce the risks to residents.
Ellicott City is indicative of many urban-suburban regions on which this nation depends. There are four action items that Ellicott City, Maryland and all vulnerable communities can complete to leverage nature to recover, plan and protect themselves:
● Estimate the flood damage benefits that green infrastructure can provide;
● Compare the benefits and the costs of using green or gray infrastructure or a mixed (green-gray) option;
● Identify the most effective options among them; and
● Target investments in conservation or restoration to the most cost-effective areas.
It is critical that we learn to design infrastructure that can serve more than one purpose. Our solutions to such disasters must align with natural processes, rather than work against them, and be adaptable to cope with changing conditions and extreme events brought on by climate change and sea-level rise.