Protect and build beaches, shorelines and islands for less than $20,000 per beach mile
by Win Wenger, Ph.D.
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This invention consists of the use of an air compressor or other source of compressed air; a hose or pipe perforated to let out a curtain of air bubbles; valves to even-out the pressure throughout the lengths of pipe or hose; and buoys and anchor-weights to maintain configurations of such pipes or hoses underwater, at appropriate locations offshore, so that when storms, high tides or turbulent currents are running, the bubbled air curtains will slow the water abruptly to make it dump its sediments where one wishes to build beach, shoreline or island.
Precursors of this system
- A similar arrangement was built upstream of Boston on the Charles River, for the much more difficult task of settling out silt and mud before they drift into Boston Harbor.
- During the 1940s and 1950s, several port cities around Italy used a similar system to keep sediments from drifting into their ports. We do not know whether this arrangement still continues.
- During World War II, many harbors used similar gear to lay air bubble curtains at their entrances, impenetrable to sonar, so that submarines would have the much riskier task of coming into the harbor directly to determine if there were any ships there worth sinking.
If you, as have most Americans, have ever seen a snow fence doing its job in winter, even though air is the fluid transport medium in this instance, you will have seen the snow drifted just to the lee of the thin line of slats of the fence. The fence slowed the wind, and the snow got dropped rather than drifting out across the road. The principle is the same.
When moving water doubles its speed, its pressure cubes, as does its ability to transport a load of sediments. The converse occurs if one can somehow intercept that water and slow it down. Beachbuilder is not only a “soft” barrier which slows the water down instead of reflecting it a la stone jetty to erode more fiercely somewhere else. It is a system easily placed and re-placed, by trial and error or until one has the configuration of beachfront that he desires, storms doing the work for him instead of eroding away his property. If one is a municipality or state or other body working on sufficient scale, the system may, with appropriate seasonal or storm currents offshore, nurture offshore shoals which later feed the beaches more conventionally. Wherever the water is shallow (and where it’s legal!), one may also build islands, not only beaches.
Some East Coast communities in the U.S.A. spend more than $15 million per winter or per year, per beach mile, trying to protect their beachfronts and generally failing. Especially is this the case for communities on the barrier islands. On April 19, 1999, The Washington Post mentioned that the Beach Replenishment Project, along New Jersey, Delaware and Ocean City, Maryland, is costing us tax payers $6 billion (that’s a B!) dollars, running some places at $20 million (that’s an M) per mile. Our Beachbuilder would run something like $2 thousand a mile. Most erosional storms are in winter. Road construction firms with air compressors for their drill hammers are mostly idle in winter. Those compressors could be rented and, by this mechanism, would account for long stretches of protected beach.
Configuration
The layout would be adapted to local conditions, given the flexibility of the system, and would be by trial and error. As a general rule of thumb, the pipes or hoses would be arranged in threes for stability, spaced and braced apart in such a way that their cross section would resemble a triangle, point downward. These triplet hoses or pipes would be buoyed and anchored every few feet or yards. Air driven through the pipes or hoses would escape through the perforations, releasing a stream of air bubbles at each hole, a curtain of air bubbles ascending from those pipes or hoses. If the main erosional threat is from currents running mostly perpendicularl to the coast, the lines of pipe or hose would lie offshore parallel to the coast. If the main erosional threat is from currents running mostly parallel to the coast, usually the hoses or pipes would lie in bunches of short lengths running perpendicular to the coast.
Hoses are mostly preferred because they are easier to lay down and take up from barge or boat, with even greater flexibility of trial-and-error placement to match varying conditions offshore. No expensive engineering is be needed, as would be the case with more permanent types of installation.
So far as is now known, Beachbuilder is far less expensive than any other system of beach protection and/or building, and far more flexible to meet changing conditions or to correct errors. Except for an occasional air compressor onshore and a hose or pipe running down into the water, the mechanics of the system make no impact upon the scene value of beach or shoreline. Where pleasure craft or fishing boats ply, buoys would have to mark the location of the lines of hose or pipe, though these would normally be below keel level.
For a process so very simple, most engineering would be ad hoc, varying from situation to situation. Municipalities may need more formally engineered systems despite changing littoral conditions. Because of that variation, even valve specifications and the size and frequency of perforations of pipe or hose will differ from situation to situation. Individual seaside property owners are mostly expected to cobble systems together from resources close to hand in any case, without formal engineering. Perhaps a firm or so, even formed for that purpose, will gain enough from experience to offer standard packages for identified categories of situation.
Pitfalls
- If water deepens too rapidly too close to shore, it becomes more expensive to amass the huge amount of sediments needed to build beach, shoreline or island. Nonetheless, the bubble curtain can still be used to protect the beach or shoreline that’s there, during storms, damping the waves and currents which are doing the eroding.
- Planted too deep in the water or in the case of a very large storm, pipe or hose may be buried by the very sediments they cause to be deposited. Planted too shallowly in the water, they are more easily damaged by wave action during the storms whose effects they are using to deposit sediments. Conditions vary from place to place, and from time to time. The system is so flexible as to make trial and error feasible; conditions vary so as to make some trial-and-error necessary. One can expect some losses of pipeline or hoseline from time to time—yet the system is still vastly less expensive than the alternatives, and more effective.
- If you leave the hose or pipeline array in the water between storms, you may wish to maintain some light positive air pressure in it to prevent sediments from working their way into the piping to block it.
- Take into account, in your placements, the normal cycle wherein the shoals nourish the beaches during normal wave action between storms, and the beaches nourish shoals during storms. Beach placement is a dynamic; Beachbuilder has to be one element within that dynamic. Nonetheless, any region of shoreline applying Beachbuilder can be expected to amass sediments during storms, including sediments otherwise normally carried out to sea and lost.
Who owns Beachbuilder?
You do. As of its April 20, 1997, release, the invention is in public domain for anyone to use freely. Who may use it freely? You or any other person, corporation, association, town or township or other community, state, nation, or organization, within such limits as are imposed by law, the well-being of others affected by your actions, and good common sense. The inventor would be pleased to consult in some way on any large-scale project.