New flood inundation maps showing which properties the Susquehanna River would touch as it rises in stages should be completed and posted online by the end of the summer, a Luzerne County official said.
The maps will help impacted residents and businesses make plans about moving belongings to an upper floor or out of a structure entirely and assist officials who must approve evacuations and road closures, county Flood Protection Authority Executive Director Christopher Belleman said Tuesday.
“It’s a tool for people living in flood-prone communities so they can make decisions on how they can prepare,” Belleman said.
The data will be particularly helpful to newcomers who did not witness what happened in their flood zone in 2011, he said.
Authority board members voted Tuesday to pay $3,200 toward the $349,000 mapping project, which will cover a 100-mile Susquehanna stretch from Sunbury in Northumberland County to the Exeter Township area in Luzerne County. The federal government is providing the lion’s share of funding, he said.
The project is needed because the current Wyoming Valley Flood Warning System developed by the U.S. Army Corps of Engineers in 2000 is obsolete, Belleman said.
The new inundation forecasting maps will be based on a federal government water analysis completed after record Susquehanna flooding in 2011, he said.
This analysis focused on the massive 10,000-square-mile watershed that drains into the local stretch of the Susquehanna. The watershed extends into the Finger Lakes and Catskills in New York.
After studying 2011 high water marks and water drainage patterns, the federal government concluded development in the northern watershed is sending more runoff into the local stretch of the Susquehanna as sediment and other changes to the river channel have reduced its water holding capacity during peak flows, officials have said.
The inundation maps will show what happens as the river rises in one-foot increments, starting with the “action stage,” project documentation shows.
This stage occurs at a river level of 10 feet in the Wyoming Valley, when officials start activating levee system pumps, Belleman said. All pumps are operational at 19 feet. The Susquehanna swelled to a record 42.66 feet during Tropical Storm Lee in September 2011.
A tool allowing officials to estimate monetary flood damages also is part of the program.
Officials will hold webinars and other public information sessions on how to access and interpret the maps when they are posted, Belleman said.
The maps, which also will cover Montour and Columbia counties, will appear on the National Weather Service website and possibly others, project documents say.
“I think it’s a great project,” Belleman said.
Belleman said he has not received notification on when the Federal Emergency Management Agency, or FEMA, will implement new flood insurance maps based on the analysis completed after the 2011 flood.
The current insurance maps were implemented in November 2012 based on data compiled before the record flood, officials have said.
The post-2011 analysis had concluded the base flood elevation has increased by 0.7 feet to 4 feet in some locations along the 100-mile Susquehanna stretch.
The base flood elevation is the estimated height water is projected to rise during a “base flood.” Commonly known as a “100-year flood,” a base flood has a 1-percent chance of occurring or being exceeded in any given year.
This base elevation determines which mortgaged properties require flood insurance, how much property owners will pay for insurance and the high-risk zones requiring tougher restrictions or limitations on construction, officials say.
