Dam Busters

Today more than ever, communities across the country face the harsh realities of dwindling resources. Be it declining revenue or increased demand on natural resources like water, governments are reexamining their management of such critical waterways to improve efficiency and environmental quality.  What may be surprising is the fact that this renewed outlook has involved the removal of hundreds of dams along the nation’s busiest waterways, allowing rivers and streams to regain their natural flow and cleanse themselves of decades of backed up pollution and sediment^.[1] As noble as these ambitions are, water management for things like residential, industrial and agricultural use remains vitally important.  With these factors is mind, the replacement of old dams with more cost-effective, inflatable ones made of vinyl coated membranes is gaining popularity.

The first inflatable dam was a tube made of ordinary rubber in the mid 1950s by Norman Imbertson for the Los Angeles Department of Water and Power.  Early on, the use of rubber limited most inflatable dams to small-scale applications at construction sites or to contain sewage runoff.  However, new technology and the recent use of stronger and more cost-effective materials like vinyl coated polymers fused with industrial grade fabric has made large scale applications more feasible.^[2]  The use of vinyl mesh is not only cheaper but stronger than ordinary rubber and allows for easy repairs by simply patching leaks in the membrane, similar to the inner tube of a tire.

When stretched across a waterway, the strength and flexible qualities of the vinyl membrane allows for flexibility with the ebbs and flows of the water or impacts from floating debris.  The dams are typically inflated with water, air, or a combination of both, providing buoyancy and stability.  The nature of the inflatable dam allows engineers to easily control water depth upstream by quickly raising or lowering the membrane’s internal pressure.  When completely deflated the vinyl tubing rests at the bottom of the streambed, allowing for the passage of fish and the release of built-up pollution and sediment, as often occurs upstream from traditional dams.^[3]

On the Susquehanna River, the world’s longest inflatable dam, the Adam T. Bower, provides flood protection for the nearby community.  When water resources become more scarce in the drier summer months, the dam is inflated, creating Lake Augusta used for recreation, groundwater recharge, and a dependable supply of fresh water for nearby residents.  In the winter when rainfall is more plentiful the tubing is deflated and the river regains normal flow.^[4]

As inflatable dams become more popular, it is examples like this that are creating a precedent for similar projects around the country.  In using more flexible damming methods and materials like vinyl, engineers are finding more effective methods for managing our nation’s water resources.

---

 

^[1] “Largest Dam Removal Aims to Bring Salmon Back,” NBC News, September 18, 2011,  http://www.nbcnews.com/id/44554709/#.UVUcLzfiRxU