Arrival of flood maps also brings good news for Harrisburgers

For Harrisburg officials, the state’s mapping of the flood zones was trumped by the arrival of the first set of studies of the interior flood threat for Harrisburg, those areas along Pankey Branch and the West Harrisburg drainage area.

The new studies show a somewhat reduced portion of the business district along U.S. Route 45 as a threatened area.

The mapping also included what will happen when a planned new pumping station is added to the Pankey Branch area.

During an afternoon session, city consulting engineer Jim Brown and engineers and hydrologists from the U.S. Army Corps of Engineers thoroughly discussed the mapping. The final result: The Corps will do some more work on computer flood models to reflect the city’s now increased impoundment area size, the Sahara impoundment and a crossover between the city’s two drainage areas.

The Corps also brought to Harrisburg good news about the levee: It will be certified.

Also relayed to the city was the Corps OK for a new pumping station that will add to the ability to de-water the drainage areas, especially Pankey Branch.

For the city, the next challenge will be to coordinate the work of the Corps with the work of the state in developing the final maps.

Brown said he believes it is important the Corps work be done and the data generated by the group be in the hands of the state before final maps are prepared in about December.

There were indications while the remainder of the county is in a 30-day comment period before finalization, state agencies and Corps will work together to produce Harrisburg’s interior maps.

With the levee certified and maps complete, residents inside the levee will find the 100-year floodplain a moot point for most purposes. While backwater flooding can occur, a certified levee will render the interior as an area without a floodplain.

Several parts of area villages and rural areas will see slight changes in the elevation of flood plains. The most consequential of the changes will involve Muddy — and it will be a good point for the village.

The floodplain of Muddy as developed by the state will be about 3 feet lower than on old maps, leaving Muddy proper an island during a 100 year flood event.

On Tuesday rural officials and officials of all incorporated areas of Saline County were able to see, for the first time, new flood risk mapping with most observers interested in the so-called 100-year flood areas.

For Harrisburg officials, the state’s mapping of the flood zones was trumped by the arrival of the first set of studies of the interior flood threat for Harrisburg, those areas along Pankey Branch and the West Harrisburg drainage area.

The new studies show a somewhat reduced portion of the business district along U.S. Route 45 as a threatened area.

The mapping also included what will happen when a planned new pumping station is added to the Pankey Branch area.

During an afternoon session, city consulting engineer Jim Brown and engineers and hydrologists from the U.S. Army Corps of Engineers thoroughly discussed the mapping. The final result: The Corps will do some more work on computer flood models to reflect the city’s now increased impoundment area size, the Sahara impoundment and a crossover between the city’s two drainage areas.

The Corps also brought to Harrisburg good news about the levee: It will be certified.

Also relayed to the city was the Corps OK for a new pumping station that will add to the ability to de-water the drainage areas, especially Pankey Branch.

For the city, the next challenge will be to coordinate the work of the Corps with the work of the state in developing the final maps.

Brown said he believes it is important the Corps work be done and the data generated by the group be in the hands of the state before final maps are prepared in about December.

There were indications while the remainder of the county is in a 30-day comment period before finalization, state agencies and Corps will work together to produce Harrisburg’s interior maps.

With the levee certified and maps complete, residents inside the levee will find the 100-year floodplain a moot point for most purposes. While backwater flooding can occur, a certified levee will render the interior as an area without a floodplain.

Several parts of area villages and rural areas will see slight changes in the elevation of flood plains. The most consequential of the changes will involve Muddy — and it will be a good point for the village.

The floodplain of Muddy as developed by the state will be about 3 feet lower than on old maps, leaving Muddy proper an island during a 100 year flood event.

Corps officials said new numbers have been generated for the amount of rain needed for a so-called 100-year flood for Harrisburg, 7.5 inches.

Those attending an afternoon session for government agencies were told the flood of 2008 that caused heavy damage to Harrisburg is categorized as a 1,000-year storm — not flood — event and is unlikely to occur again.
Rainfall in 2008 was 11 inches.

The new state Department of Natural Resources-developed flood maps, when completed, will cause many communities to reexamine entry into the National Flood Insurance Program.

Loans made on properties within a flood zone will require flood insurance and to get the insurance at a reasonable government-set rate, municipalities must have entered the insurance program.