Since 1968, the Wyoming Valley Levee Project prevented more than $7.6 billion dollars in flood damages in Luzerne County, Pa.
The 16 mile project consists of three levee systems: Kingston to Exeter, Wilkes-Barre/Hanover Township and Plymouth. In addition to the earthen levee and floodwalls, the project contains 13 stormwater pump stations, 39 pumps, 20 closure structures and 130 relief wells.
In 2013, the U.S. Army Corps of Engineers, Baltimore District evaluated the project. This evaluation showed the project is structurally sound and sufficiently maintained. During Tropical Storm Lee, which impacted the area in 2011, the levee project successfully contained the river, estimated by the U.S. Geological Survey at a peak flow of 310,000 cubic feet per second. This is the highest discharge event that the raised levee project has experienced. While there were some damages, which were repaired, the levee systems were not overtopped and did not fail.
A recent Corps of Engineers analysis that incorporated Tropical Storm Lee data verified that peak flow estimates have increased for the Susquehanna River. The main cause points to the increase of the frequency and severity of storms causing floods over the last 25 years. Given the probability of future flooding is based upon historical events, this trend has increased the predicted flood risk.
In addition to more rain, flood risk has also increased with land development that creates impenetrable surfaces that prevent water saturation into the ground and removes natural features like wetlands, which help contain water. Additionally, natural and development changes to the river channel have reduced how much water is contained within the river banks during peak flow periods, thus increasing flood risk.
What are the impacts?
The district team, along with representatives from the Federal Emergency Management Agency Region III and the Luzerne County Flood Protection Authority, recently briefed the Wyoming Valley community on the impacts of these findings.
“Because of these changes the Plymouth and Wilkes-Barre/Hanover Township levee systems lack the required amount of freeboard, which is additional height added to a levee to provide a required safety factor,” Harvey Johnson, the district’s chief of the Civil Works Branch, told attendees. “This prevents the Corps of Engineers from evaluating that the two levee systems meet FEMA and Corps of Engineers levee accreditation requirements. This means a potential change to the area’s zone designation on the flood insurance rate maps.”
In order to map the flood risk in areas where there are levees, FEMA and the Corps of Engineers requires a levee system to meet a set of performance standards. When these standards are met, FEMA accredits the levee as protecting properties behind the levee from river flooding during the 1 percent annual chance flood event. This protection is depicted on Flood Insurance Rate Maps (FIRMs).
When these performance standards are not met, the levee is not accredited and not shown on the FIRMs as providing protection from the 1 percent annual chance event. This performance standard for mapping risk is currently undergoing changes with the introduction of a new Levee Analysis Mapping Procedure (LAMP), being initiated by FEMA.
“LAMP is designed to recognize some risk reduction by a levee under some conditions that would not allow it to be accredited,” Gene Gruber, Mitigation Division Director for FEMA Region III, explained during the meetings.
The Wyoming Valley Levee Project, when raised between 2001-2006, met the FEMA performance standards and was depicted on the FIRMs as providing protection from river flooding at the 1 percent annual chance event. In 2011, based upon the need to periodically verify previous levee accreditations, FEMA issued a request to the Luzerne County Flood Protection Authority for levee evaluation data necessary to confirm that the levee systems remain accredited.
In 2013, the Corps of Engineers, on behalf of the Luzerne County Flood Protection Authority, initiated this evaluation, which resulted in a set of levee evaluation reports. These reports were completed in March 2014 and provided to FEMA and the Luzerne County Flood Protection Authority.
The report recommended that FEMA accredit the Kingston-Exeter levee system, but not the Wilkes-Barre/Hanover Township or Plymouth systems because there was not enough freeboard.
Over the next several months, FEMA will begin to institute the first of the four-step LAMP process, leading to mapping of the level of protection from flooding risk that each non-accredited levee provides. This process is new and will include a Local Level Partnership Team (LLPT) comprised of federal, state and local officials and levee owners. This engagement will enable FEMA to make a better-informed final decision, using local input on how the levee system will be analyzed and how the flood hazards in the area landward of the levee will be mapped.
Additionally, the Corps of Engineers will continue to carry out tasks associated with the Levee Safety Program. This includes completing annual inspections, risk assessments (levee screenings), and periodic inspections (more in-depth assessment completed every five years). All inspections are done in coordination with the Luzerne County Flood Protection Authority, who operates and maintains the Wyoming Valley Levee Project.
“I wish to extend a huge thank you to my friends at the U.S. Army Corps of Engineers and FEMA for taking time out of your very busy schedules to make the three trips up to northeast Pennsylvania for the local officials and public presentations,” said Chris Belleman, executive director for the Luzerne County Flood Protection Authority. “Your presentations on the revised flood hazards were excellent. The feedback that I have received has generally been positive. We will continue to educate the public and allow the LAMP process to be rolled out.”