Sunday, November 3, 2013

Delta Crossings

Cold, dry air from the north crosses warm, damp air from the south over the United States’ mid section, an area known as “Tornado Alley.” This is the only area in the world that regularly sees tornados. These storms occur in greatest frequency as seasons change in the spring and fall. A tornado struck the Arkansas Delta town of Caraway tearing down trees, utility poles, and power lines. A number of homes were heavily damaged. A beekeeper friend’s home sat in the storm’s path; it sustained minor damage. The beekeeper and his wife ducked safely into their storm shelter as the storm struck.  Large trees fell around them. The beekeeper checked on family, friends, and bee hives; all survived the storm. Beekeepers often divide their bee hives among several bee yards to lessen the losses from catastrophic events like fires, floods, or wind storms.

Caraway sits between the Mississippi River and the St. Francis Sunken Lands, a depression formed during one of North America’s most powerful series of earthquakes. In the winter of 1811 through 1812, earthquakes shook the area, transforming the surface of the land. The soil liquefied, and sand blew high into the air. The Mississippi River flowed backwards to fill large depressed areas which became lakes. Today, flooding in the St. Francis Sunken Lands area is controlled by a series of earthen levees, natural rivers, and man-made canals. South of Caraway where opposing winds crossed, two rivers cross in an amazing engineering feat. At Rivervale, Arkansas one river, a channelized canal, flows in a concrete tube under the St. Francis River. The rivers’ crossing can be seen in today’s photo. The concrete tube is visible horizontally under the surface of the St. Francis’ waters. Nearby, the Marked Tree Lock and Siphons are unique water control designs; the Siphons are the only structures in the United States where tubes are used to lift a river over a levee. The St. Francis River is lifted out of the Sunken Lands.