County to host open house for new floodplain maps

Nov. 14--WEST OLIVE -- Anyone in Ottawa County who buys flood insurance or lives in an area close to people who need flood insurance may want to attend an upcoming open house to review possible changes to area floodplain maps.

The Federal Emergency Management Agency (FEMA) will host the open house from 5-7 p.m. Wednesday, Dec. 4, in the Ottawa County Emergency Management Training Room, located at the county's Fillmore Complex, 12220 Fillmore St., West Olive.

At the event, you can review the updated preliminary flood insurance rate maps and learn about your risk of flooding and how your property may be impacted by it. FEMA representatives will be on hand, as will representatives from various local, state and federal agencies to provide the most current information about flood risk, flood insurance, floodplain development regulations and the process for floodplain mapping within Ottawa County, officials said.

Once the new floodplain maps become effective, they will be used as the basis for flood insurance ratings as well as local flood protection regulations adopted under the National Flood Insurance Program. The majority of this will be along the coastal flood areas such as the Lake Michigan shore and the Grand River, according to Ottawa County Emergency Services Director Nick Bonstell.

"You might want to check if you live in a floodplain," Bonstell said. "Areas shift a little."

Over the past few years, FEMA has been studying the Great Lakes and working toward creating new floodplain maps, officials reported in a newsletter to Grand Haven Township residents.

The Great Lakes are not tidal like the oceans, meaning the water doesn't have a cyclical rise and fall caused by gravity between the earth, moon and sun. Rather, the Great Lakes experience seiches. A seiche is basically a standing wave that oscillates back and forth. If you have observed water sloshing back and forth in a swimming pool or bathtub, you have witnessed a small-scale seiche.

Seiches are typically the result of strong winds and rapid changes in atmospheric pressure, pushing water from one end to the other. When the wind stops, the water rebounds back to the other side. This continues for hours to days, and resembles a tide.

FEMA has determined that when you combine the wind and oscillation, you can get "velocity hazard," or wave action, that runs up the shoreline. This wave action causes two major problems that we're all too familiar with right now -- erosion and ponding. As the waves continually run up the shoreline, the ground becomes saturated, resulting in water ponding to a flood depth of 1-3 feet.

Because the Great Lakes are the only ones of their kind in the world, scientists and engineers have had a difficult time creating the Flood Insurance Study (i.e., the work done to create the preliminary floodplain maps). The Great Lakes are unpredictable, and the proposed floodplain maps will now try to account for the localized flooding that occurs on the Lake Michigan shoreline.

Digital files of the preliminary maps and FIS report can be downloaded at www.fema.gov/preliminaryfloodhazarddata.

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