Infrastructure and the Environment: Mitigating Flooding in Baton Rouge

BY BETSY GARDNER • NOVEMBER 30, 2021

 

In 2016, a summer storm inundated Baton Rouge and the surrounding region. According to the Red Cross, this was the worst natural disaster in the country since Hurricane Sandy, which had struck the New York area only four years before. In just a few days, more than 90,000 homes were damaged or destroyed, 28,000 people had to be rescued from the flooding, and several residents died.

 

While this unnamed storm didn’t garner the same national attention as Hurricanes Harvey and Sandy, the city and parish of Baton Rouge immediately began to develop plans and preparations for dealing with future flooding, in hopes of preventing further displacement and death. Warren Kron, the city’s GIS Manager, had previously developed maps to support watershed-based planning in 2010, work which unfortunately didn’t have much support until after the 2016 flood. During the flood, the city’s GIS team was working round-the-clock to map where the water was the worst to determine where residents were dealing with severe housing damage and how disaster services should be distributed. To supplement city data, the team asked residents to share photos of local conditions on social media, a request that folks quickly responded to.

 

Photo of a Baton Rouge street that is completely floodedKron’s team built a GIS map of the Estimated Flood Inundation Area based on data from “911 calls, Baton Rouge Fire Department search and rescue data, 311 requests for service, street-level damage assessments from city-parish staff and other public officials, debris collection routes, road closure information, NOAA imagery, Civil Air Patrol imagery, FEMA DFIRM flood hazard areas,” and the citizen-generated photo data. According to Kron, the map ended up being a fairly accurate representation of the inundated area and it is a map that people still refer to when buying a house in the area.

 

 

Planning and Prevention

With the context of this major disaster, proof that GIS flood mapping is useful and relevant, and a new city-parish administration, Baton Rouge was ready to tackle flooding and rainfall with an organized, data-driven plan. Mayor Sharon Weston Broome took office in January 2017 and immediately sent out a request for proposal (RFP) for a Stormwater Master Plan. The infrastructure firm HNTB won the contract later that year and began to analyze data and identify gaps. According to Kron, the city’s robust data repository didn’t yet include comprehensive stormwater asset data or an overall parish-wide model to identify current infrastructure projects, both of which would be valuable data that could influence planning.

 

All of the land cover, elevation, channel surveys, and subsurface systems/conveyance data that HNTB either compiled or collected was eventually fed into a computer model used to evaluate flooding scenarios. Melissa Kennedy, HNTB’s senior project manager for the Stormwater Master Plan, built a virtual model that would simulate various flooding events, to determine “what floods where, how much, how deep and the resulting damages.” The powerful model can predict and display flooding and rainfall based on a host of changeable factors, like rates of emissions, dates, climate change progression, and rainfall levels. The city has a steering committee that helps guide these projections, a group that includes the state climatologist and North Carolina State Professor of Marine, Earth and Atmospheric Sciences Kenneth Kunkel. During the committee's monthly meetings they review things like NOAA rainfall data, updated climate change futures values, and infrastructure projects to build capacity.  

 

One of the GIS layers is the subsurface system, or the underground pipe and drainage network. The 12 survey teams that HNTB deployed not only identified the locations of assets but also noted the conditions; the city hadn’t previously collected data like this, but the dual data on location and condition are crucial for building a climate-resilient city and parish. HNTB also used the city’s building footprints dataset for measuring where and how structures are affected by water levels, in order to gauge what aspects of the city-parish stormwater system are resilient to climate change. 

 

According to Jeff Doudrick, senior technical engineer at HNTB, this new model will inform how the city builds and prioritizes infrastructure projects in the future. Mapped assets include homes, schools, fire and police stations, pump stations, and water treatment plants, plus primary roads used for emergency vehicles and evacuations. All of these assets are tested in the virtual model to ensure that city-parish officials are aware of high-risk flood areas, which can be addressed with more resilient architecture in the near future. As Doudrick explained, it’s better for a street to flood than a house, but the depth and duration of street flooding has to be modeled so that officials understand the impacts on emergency services in high-risk flood areas.

 

Data and the People

All of the surveyed stormwater asset data was compiled and thoroughly checked by HNTB and then shared with city employees through an online mapping portal within one day after it was collected. Once the data collection phase was completed, HNTB delivered it to the city-parish government as per the terms of the initial agreement and now the city’s GIS team manages the data and has built applications for employees to put the information to use in their daily operations.

 

In order to identify the high/medium/low risk areas and populations within the various parish neighborhoods, one of the datasets that the city-parish wanted to include for flood modeling was Social Vulnerability. Residents have been very supportive of this work; Doudrick said that the Baton Rouge city-parish is the most engaged community he’s ever seen during his time doing floodwater work in the country. Having been through numerous flooding events and storm disasters, community members were willing to engage with different public stakeholder meetings, submit input, and even volunteer as trusted community messengers to discuss the plan within their communities. While the pandemic did force a lot of this work online, residents remained very involved and are now seeing the final flood hazard assessment. The city-parish is asking for input on the assessment, and residents will continue to have the opportunity to share photos and documents about flooding in their homes and businesses. 

 

Another group of engaged community stakeholders are land developers and builders; future builds and development proposals will need to utilize the data and models in order to plan developments that won’t negatively affect the local stormwater management and infrastructure, or established buildings in the area. The city-parish hopes to have all this data available to the public in the very near future, and potentially use it to conduct FEMA flood zone remapping or to revise zoning regulations.

Funding Back Better

FEMA has already been involved in the work through funding, as HNTB was granted parish-wide funding for this Stormwater Master Plan project. Baton Rouge is unique, as it’s a city-parish, and the city proper is surrounded by three other mayor-managed municipalities. However, extreme rain and flood disasters affect the areas simultaneously, and therefore many of the mitigation and prevention strategies follow watersheds that cross jurisdictional boundaries. There is also strong motivation for working together and data-sharing across the greater Baton Rouge region, as overflow water from the Amite River, Bayou Manchac, Comite River, Mississippi River, and Thompson Creek affect land in all of the municipalities.

 

Once the Master Plan is complete and the city-parish moves forward with the identified projects, funding will likely be a blend from the Louisiana Watershed Initiative, FEMA, the state water commission, and the new American Rescue Plan Act (ARPA) and infrastructure bills. The types of projects will likely include the creation of detention ponds, changes to subsurface pipe systems, stream channel widening and clearing, and flood plain preservation. The idea is to balance out the whole interconnected system and find ways to detain water upstream before lower elevations of the parish are inundated, another reason why the funding will be a blend of federal, state, and local resources as it works across several rivers and watersheds. 

 

The Department of Homeland Security is also working with the city-parish to buy out repetitive loss properties, which FEMA defines as a property that has had “two claims greater than $1,000 in any 10 year period since 1978.” Once the city-parish government purchases these properties, they demolish the structure and preserve the property as green space, which could potentially serve as detention ponds in the future. Looking at the data, a map shows a piecemeal of city-owned property, but local officials hope to move toward a more organized process of purchasing a larger block of repetitive loss properties in order to create larger water detention areas.

Baton Rouge of the Future

The overarching goal of all this work is to provide the city-parish with a 20 year capital improvement plan for a safer, more resilient Baton Rouge. HNTB will provide recommendations for projects and policy recommendations, plus an outline of the project costs, potential funding sources, and a work schedule — all tied into the digital map. 

 

Based on the existing data, the city-parish already has some ideas for improving resiliency; for example, the maintenance of the subsurface system will become a more proactive service. Typically cleanouts were based on 311 citizen submissions and one-off requests for service, but with condition data of the entire subsurface system, the city has already begun responding proactively instead of reactively. 

 

The city-parish will also look into changes to housing and land development codes, as preliminary revisions and recommendations identified green infrastructure and conveyance checks as important parts of a holistic, watershed-based approach. The city-parish will also need to find new ways to prevent flooding; one option is to require structures to be built farther away from the very edge of waterways to conserve the riparian buffer. Recent floods have proven that the current proximity allowance is too risky. But with 50 percent of East Baton Rouge within a flood hazard area, the city-parish will also need to find ways to improve code requirements in a manner to build and redevelop smarter and greener.

 

The future of Baton Rouge is looking safer — and drier — thanks to this intensive data collection, mapping, and analysis. As cities across the world face changing climates and more intense natural disasters, Baton Rouge is leading the way with data.

 

Body image from climate.gov, August 19, 2016

About the Author

Betsy Gardner

Betsy Gardner is a writer for Data-Smart City Solutions and the producer of the Data-Smart City Pod. Prior to joining the Ash Center, Betsy worked in a variety of roles in higher education, focusing on deconstructing racial and gender inequality through research, writing, and facilitation. She also researched government spending and transparency at the Lincoln Institute of Land Policy. Betsy holds a master’s degree in Urban and Regional Policy from Northeastern University, a bachelor’s degree in Art History from Boston University, and a graduate certificate in Digital Storytelling from the Harvard Extension School.