January 11, 2013

Coastal flooding is real


Crab shack on Tangier Island
Virginia Institute of Marine Science (VIMS) calls for a flexible, multi-step approach to flood risks in Tidewater Virginia. Click here to read the entire report.

VIMS also offers the public an excellent free opportunity at 7 p.m. on Thursday, January 31, to learn more about recurrent coastal flooding. Molly Mitchell, VIMS researcher, will present potential adaptations and options for our flood-prone Tidewater area. Call 804-684-7846 to register for this free program, over the Coleman bridge at Watermen’s Hall, 1375   Greate Road. Gloucester Point.

The best book I have read about coastal flooding and the resulting erosion is William Cronin’s “The Disappearing Islands of the Chesapeake.” Cronin presents survey results of forty-odd islands that are either submerged completely or eroding at an alarming rate each year.

Locally, the Guinea Neck neighborhood of Gloucester County and the Poquoson area of Hampton Roads are very prone to flooding in almost every heavy rain. After Hurricane Isabel, many Guinea Neck homes were raised by a few feet, owners hoping to buy a little time and distance from the York River.

As a sailor, I have seen low lying islands succumbing to sea level rise. Holland Island used to be home for 300 hardy watermen and their families; most left in the early 1900s. But the last house on Holland Island collapsed in October 2010, finally succumbing to storm waves and erosion.

Grog Island (in Fleets Bay north of the Rappahannock River) is one that we saw first in 2002. The cruising guides even recommended it as a great "lunch hook" drop--not protected enough for an overnight anchor, but delightful as a place to go ashore for a picnic lunch. Then we saw it after Hurricane Isabel when only a few scraggly pines remained. A few years and storms later, only a few dead tree tops. And in 2012, nothing but a few stakes to mark the "easy to run aground" spots.

Hart and Miller Islands, off Baltimore's Back River, are the opposite extreme. In spite of erosion, we sailors used to dinghy ashore for picnic lunches back in the early-1970s. Then the Maryland Department of Natural Resources bought the land in 1975 and proceeded to fill it in with dredged material from Baltimore's channels. Millions of yards of dredged material later, the now hyphenated Hart-Miller Island is a thriving wildlife sanctuary and recreation area for boaters.

Smith Island and Tangier Island (really groups of islands) are the two inhabited Chesapeake Bay islands most threatened by rising waters. In the 1980s, a seawall of boulders was erected along a stretch of the western shore of Tangier, and it succeeded in keeping a small airport and the town's sewage-treatment plant from being lost to the Bay. Another $3.6 million jetty project was approved by the Army Corps of Engineers in 1996 but it remained undone. Fourteen years later, in November, 2012, Governor McConnell had good news for the residents who have been lobbying for another jetty/ seawall to save the harbor. But now its budget is $4.2 million, with the federal government paying for about $3.2 million. To an island that is losing up to 19 feet of land every year, that was welcome news. But the islanders may not see it for a few years.

More about Poplar Island, James Island, and Tippety Wichety Island in the future. And then there are the islands of Tuvalu in the Pacific and the Maldives in the Indian Ocean where rising oceans will force the inhabitants to relocate.

How can we know when to evacuate? Coastal communities such as ours have less time to adapt if sea-levels rise faster.  William & Mary’s Virginia Institute of Marine Science (VIMS) developed a Tidewatch system to forecast coastal flooding, measuring the difference between predicted astronomical tides and observed or real-time water levels. That’s the one that includes storm surge. When our local winds shifted during Superstorm Sandy, Tidewatch detected the drop in water level before the Weather Chaneel’s computer models. You can check it out at www.vims.edu/bayinfo/tidewatch