REGIONAL – At the Ulster County NY Rising Community Planning Committee meeting on Monday, December 16, the focus was squarely on flood prevention, a topic much on the minds of local leaders ever since the one-two whammy of Tropical Storms Irene and Lee.

NY Rising is a state effort to put funding, as much as $3 million per municipality, to work on such things as flood mitigation and repairs to needed public facilities.

Ron Miner of CDM Smith, a Massachusetts engineering firm, gave a presentation on computer flood modelling, which the committee is looking to purchase to form the basis for mitigation planning. Flood modelling would identify not only those places in the Rondout Watershed that are likely to cause problems, but also the places where money might best be spent to achieve worthwhile results.

Computer flood modelling is a fairly recent development and Miner began by separating two concepts that many of us confuse when talking about water and landscape: Hydrology concerns rainfall and runoff. Hydraulics is how water flow is routed through streams and rivers. He further explained that flood modelling involved building a mathematical representation of the rainfall and routing of water as it passes through a drainage area. Of course, flood studies assume clear channels and structural openings, as under bridges, being free of debris.

Flood reduction options come down to two prime choices: Increase storage systems to retain water and reduce peak flow rates during a flood event and/or increase 'conveyance' to reduce the depths of flood water.

In this context, Miner explained some important points about reservoirs.

"The only way reservoirs work in flood reduction is when they're empty when it starts to rain," he noted, pointing out that reservoirs come in two broad varieties — flood control and water supply. The reservoirs in the Rondout watershed, of course, are water supply reservoirs for New York City.

Lenny Distel, incoming supervisor for the town of Wawarsing, brought up New York City's failure to draw down the water level in its reservoirs during Irene and Lee, which led to large amounts of water going down the spillway.

There was discussion of the distinct differences between the D.E.C., which is the statewide environmental control agency, and the D.E.P., which is centered on New York City and its concerns.

Discussing flood mitigation efforts, Miner noted that modifications to channels and flood plains were an area worth concentrating on. He listed things such as the replacement and retrofitting of bridges and culverts, construction of diversion channels and conduits, removal of encroaching structures, building of flood walls with flap gates around vulnerable buildings, and even raising of structures above flood levels.

To model for all of these problems and mitigation efforts, the data set would come from topographic maps, LIDAR scans (airplane radar scanning of the terrain), detailed studies done by FEMA, and field studies involving measurements of stream depths, flood levels, bridge capacities etc... as well as community meetings.

Miner stressed that the archive of data held by communities could be both highly informative in this context and worth a great deal of money in terms of what could be saved in project costs.

During discussion, Steve Kelley of Ellenville Regional Hospital mentioned that a map of the reservoirs showing the levels of drawdown required ahead of storms of varying expected intensities would be useful. Miner replied that they could simulate how much the reservoir should be lowered for various level "events" such as a 120 year flood.

Nina Peek, who is working to coordinate the Ulster County NY Rising effort, said that of the 40 or so projects now being considered by the committee in individual towns, modelling could show where the most value could be obtained.

Also mentioned several times was the fact that, as one speaker put it, "Cooperative multi-jurisdictional projects" look good on the application. There are also extra streams of funding, as much as $9 million in addition to the $3 million municipal amounts, available for projects that bring together two or more towns on regional watershed needs.

Peek concluded the meeting saying that the next would be on January 6, again at the Ulster County Community College Business Resource Center in Kingston, and focused on discussing the results of risk assessment for asset inventories which include all the assets identified by the ten municipalities that are vulnerable to flooding now working together for the one-time state funding.