Over time, this can lead to the formation of large sand bars.Īt first glance, air bubble screens may seem like too weak a force to counteract these currents, but as Anton Schleiss from EPFL's Laboratory of Hydraulic Constructions explains, they are able to do so by unleashing a much stronger force. In doing so, they can erode sediments from the outer bank of the river and draw them inwards. These weaker currents run perpendicularly to the flow of the river.
Where rivers bend, secondary currents form. They published their findings in the Journal for Hydraulic Engineering. According to their tests, bubbling air from the riverbed could counteract the currents that form the sand bars. Air bubble screens could be a viable alternative to costly dredging operations, which are currently relied on to keep the river open, say researchers from EPFL, the University of Delft, and the Chinese Academy of Sciences. In river bends, secondary currents can cause these channels to become partially obstructed by sand bars that are formed as sediment is drawn in from the outer side of the bend. In its shallower segments, ships are restricted to deep underwater channels. Army Corps of Engineers is overseeing the work.The Rhine River is a crucial transport artery, carrying hundreds of millions of tons of freight each year. The $22.8-million beach renourishment is a joint federal, state and local project. Since crews are working 24 hours a day, he expected to be back on the job shortly after sundown. "The main generator blew a turbo charger," said J.M.
A second unloading was delayed for eight hours after an equipment breakdown Thursday afternoon. Only one barge load of sand, about 2,000 cubic yards, reached Belleair Beach on Thursday morning. The unloader has a metal snorkel attached to it that reaches down into the sand-filled barges, scarfs up the sand and then sends it down the pipes toward the shore. What Barth saw is called an "unloader." Weeks Marine, the New Jersey company that is refurbishing the beaches, built the unloader especially for this project, said David Guillot, project manager for Weeks. Wednesday when he looked out the window of his condo and saw a large piece of equipment anchoring about 3,300 feet off the Belleair Beach coast. Sand Key resident Bob Barth said he knew the first of the sand was on its way about 7 p.m.
Clary and others hope a broad beach of about 130 feet will provide a buffer between homes and raging saltwater and wind when storms hit.
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