DC Prepares for More Flooding, Climate Change

Kierstyn Schneck

April 30, 2015

Washington, D.C.– Residents of the District of Columbia should expect to get their feet wet in the upcoming years and not metaphorically.

The District is on the National Oceanic and Atmospheric Administration’s list of cities set to experience routine flooding due to rising sea levels. According to the World Meteorological Organization, nations have been experiencing more extreme weather and rising sea levels, all signs of climate change. The global mean sea level could rise up to six feet in the next century, according to the National Oceanic and Atmospheric Administration, and most areas near the coast, including the District, could face 30 or more days of flooding by 2050.

The District government, along with the Metropolitan Washington Council of Governments, is working with the Georgetown Climate Center to prepare a plan for this wet future.

The Georgetown Climate Center works with state and local governments to help them update their climate, energy and transportation policies, according to its Adaptation Program Manager Jessica Grannis.

“They [District government officials] know that they have a current flood problem, and that problem is only going to get worse over time,” Grannis said. “We’re helping them think through what some of the strategies are that they can adopt and can help them mitigate those flood risks.”

The Metropolitan Washington Council of Governments is an association working on regional issues affecting the District, Maryland and Virginia and is also collaborating on this project.

What are the flood risks?

The current flood problem for the District involves three types of flooding: tidal flooding from the Chesapeake Bay; surface flooding from stormwater; and river flooding from the Potomac River and the Anacostia River and its tributaries.

Any area near the river and streams is expected to experience routine flooding. However, flooding isn’t limited to areas near water sources; low-lying neighborhoods are still susceptible to interior flooding during large storms.

While DC isn’t as at risk for extreme weather as other cities, hurricane Sandy proved it isn’t as immune as everyone thinks, according to floodplain manager Phetmano Phannavong of the District Department of the Environment.

“The probability is probably lower than other areas along the coast, but our consequences are very high,” Phannavong said. “How can we ignore the cost of all these cultural and historical artifacts and government shutting down?”

Areas most affected by flooding are Anacostia, Bloomingdale, LeDroit Park, Rock Creek Park, the Georgetown waterfront and the National Mall.

Each neighborhood requires a different approach when preparing for flooding, according to climate program analyst Kate Johnson of the District Department of the Environment.

The strategies Georgetown Climate Center are developing for the District depend on many different factors, including economic limitations, ongoing development status and environment improvement opportunities.

New construction determines how to prepare

The local government can dictate how new buildings should be flood proofed, according to Johnson, through building codes.

The District government requires builders to keep at least 20 percent of the site green, according to the District Department of Consumer and Regulatory Affairs. This department is responsible for permits, building codes and zoning codes. By including a green roof or small garden, builders can reduce the amount of stormwater that would end up in the drainage system, Johnson said.

While some neighborhoods are experiencing new construction, others are not. Preparing those neighborhoods focuses less on enforcing building zoning codes and more so on expanding the drainage system.

This system is managed by DC Water, which is currently building tunnels underneath the Anacostia River and the Potomac River to increase the capacity for stormwater that can make it to its wastewater treatment facility in Blue Plains.

“We are a dense, urban environment,” Johnson said. “When there’s a lot of rain, that stormwater needs to go somewhere and we have old stormwater systems that can’t drain it quickly enough, and that’s where you see flooding in the areas of the city that are no where near the rivers like Bloomingdale and LeDroit park.”

Other areas of the District, such as the National Mall, make use of the levee system to reduce flooding. The levee structure at 17th street was completed in the fall as a barrier in cases of high water flooding from the Potomac River and is currently under testing.

Being green can reduce flooding

While bigger, better pipes take water away, the District also looks for opportunities to create green infrastructure.

Green infrastructure is using the natural environment to help retain runoff water, rather than letting it flow into the storm drainage system, Johnson said. Green roofs and restoration projects can be examples of this type of flood reduction tactic.

An example of green infrastructure near Union Station in Washington, D.C.

An example of green infrastructure near Union Station in Washington, D.C.

Cleaning up streams and reintroducing native plants can reduce the chance of flooding, though these projects have alternative purposes of water quality and habitat restoration.

Tunneling is more effective in taking away stormwater and surface flooding, according to DDOE environmental protection specialist and project manager Josh Burch, but stream restoration takes into consideration what effect that would have on the environment.

“When tunneling, you are completely taking away that surface flow and putting it in a pipe somewhere, whereas with the natural stream restoration project you’re still trying to keep the water above grade and just try to manage it better,” Burch said. “Tunneling might decrease flood issues, but you’re taking that water away from the surface, which could also decrease habitat area.”

 

Outdated flood maps won’t prepare the District for climate change

Other factors the District needs to consider involve who is considered to be in the flood hazard area, as defined by the Federal Emergency Management Agency’s flood maps.

The District’s flood map was last updated in 2010 and shows where flooding will occur based on historical data only. It does not take into account sea level rise or changes in precipitation.

In order to factor in how climate change will change where and how much flooding will occur, the District Department of the Environment needs a forward looking flood map, Johnson said.

The flood map also determines who is required to purchase flood insurance, as part of the National Flood Insurance program. This means that residents who don’t live in the flood hazard area as shown in the FEMA flood map are not likely to have the insurance to cover damage in cases of flooding.

Federal Emergency Management Agency data, 2013

For example, Bloomingdale is not considered a flood risk, according to the FEMA map. However, Bloomingdale residents experienced property damage during the floods in 2012. The neighborhood had to request a relief fund for the damage caused because flood insurance is not required in the area.

FEMA is working on a pilot project with the District government to see what the flood insurance map would look like if it did consider climate change. However, the intent of the project is not to update who is required to purchase flood insurance, according to Phannavong, who works on the National Flood Insurance Program for the District. FEMA will not require any changes, Phannavong said, but once the project is completed by the end of summer, the District could decide to use the pilot project to update the requirements on its own.

Who can’t afford to prepare

The District government needs to consider the economic implications of their policies and projects, especially for lower income areas, according to Grannis.

Bigger, non-residential building projects in the District have to be certified to be energy efficient and to conserve water, according to the District Department of Consumer and Regulatory Affairs. This can be a costly requirement.

The Georgetown Climate Center is working on how the District could get incentives, such as rebates for green infrastructure, and on how it could reduce flood insurance rates for District residents, according to Johnson. By exceeding the standards of the National Flood Insurance Program, the District could reduce the rates by up to 45 percent, according to FEMA.

With the help from the Georgetown Climate Center, the District will have to consider what areas are the most vulnerable to flooding because of the lack of resources. The District government is looking for different ways to target initiatives residents in those areas, according to Johnson.

“You can imagine how much more difficult it is if you’re already struggling financially and your basement floods,” Johnson said. “Maybe you are able to rent that basement and that’s how you have the income you need month to month.”

Not everyone at risk has flood insurance to cover possible damage, Johnson said, and for these residents, education is key.

“Just because you’re not in a floodplain doesn’t necessarily mean that you’re never going to experience flooding,” Johnson said, “and that you shouldn’t be planning and trying to mitigate those risks.”

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