Watershed Study Assesses Flood Risks in an Effort to Avoid Damages

Delaware, Sullivan and Orange County communities in the Delaware River watershed will soon have a new tool to assess their flood risk, Federal Emergency Management Agency (FEMA) officials said this week.

“Following the Hurricane Ivan flooding that occurred last fall, we tasked the U.S. Geological Survey (USGS) with conducting a $160,000 high water mark study along severely impacted streams,” said Federal Coordinating Officer Marianne Jackson of FEMA. “The USGS personnel are the recognized experts in performing this kind of study,” she added.

During the study, USGS field staff noted and surveyed evidence of floodwater elevations, or high water marks, at sites along the Delaware River and its tributaries. Sites were chosen based on knowledge of local flooding characteristics and damages suffered during last fall’s storm.

Data were collected at a total of 50 sites between the Town of Colchester, Delaware County and the City of Port Jervis, Orange County, N.Y.

The study indicates that in some locations, such as the hamlet of Downsville, flood elevations associated with Hurricane Ivan exceeded the base flood elevation, the minimum elevation required by local law for new residential construction in a floodplain.

In other locations further downstream, such as the City of Port Jervis, flood elevations were less than the base flood elevation, despite the damages caused by the floodwaters.

Such observations emphasize the need for communities to require elevation of structures located near streams, creeks and rivers.

The high water mark study facilitates comparisons between models of flood conditions and the conditions during the storm. Public safety officials make such comparisons to evaluate the efficacy of studies and maps depicting flood risks, hoping to reduce the loss of life and property through prudent management of floodplain areas.

Information from the USGS study is being used to update products of the National Flood Insurance Program (NFIP). Property owners along the Delaware River from Colchester to Port Jervis also can reference the study to understand the magnitude of last fall’s event.

“Communities in the upper Delaware River Basin in New York can avail themselves of the most recent data on flooding and use that to help better prepare against future flood damage,” Jackson said.

Copies of the high water mark study will be available for review in the office of the community floodplain administrator, as well as available on the web at ny.water.usgs.gov/pubs/of/of051166/

Provisional USGS streamflow data also are available at http://ny.waterdata.usgs.gov.