When an AquaDam® is used to cofferdam or divert flowing water, some consideration must also be given to the velocity of the water. During installation, the AquaDam® is being installed by filling it with water, causing it to unroll across the stream channel. This causes the water flow to back up and increase in water depth. The water velocity around the end of the AquaDam® is greatly increased. Depending on the firmness of the stream / river bed that the AquaDam® is being laid over may cause some undercutting around the end of the cofferdam as it is being installed. This will result in an increase in the depth of the water to be retained, and should be considered in the above analysis when determining the maximum water depth. Velocity of the current will also play an important part in the installation of the AquaDam®. Water head will build up on the upstream side, and water on the downstream side will flow away before the completion of the AquaDam® installation.
AquaDams® can be installed on top of most types of soils or fluvial materials, including flat lying bed rock, mud, sand, gravel, small rocks, and vegetation. Select a site that is smooth, flat, and void of wire, rebar, sharp objects, garbage, glass or dead vegetation containing tree branches, etc. The slope of the riverbed should also be relatively flat or inclined in the direction of the upstream or contained water. Make sure to check the installation course for holes, obstructions or washed out areas that may cause problems during installation.
Local wet seasons and thunderstorms effect water levels in rivers, lakes, and wetlands and are important to understand during your construction Project. Projects that have flexible construction dates should be coordinated with favorable weather conditions that avoid high water levels. Water depth being retained by the AquaDam® should never exceed the recommended maximum water depth during the life of the project, not just the day you install it.
All of the previous factors are important considerations once the site has been selected. The following are additional factors that may influence the site selection.
A location on a wide, shallow river is easier to cofferdam than a narrow river channel. Wide rivers will allow a diversion with only minor increases in water depth. A narrow river will quickly increase in water depth. The larger and wider the diversion channel, the less water depth will increase.
An extremely rugged alpine river bed (such as the Eagle River) with large angular boulders within the stream bed is a difficult area, since a good tight seal can only be accomplished through the removal of said boulders by hand or heavy equipment. In the case of the Eagle River, the boulders were scraped into a line, and the AquaDam® was installed directly upstream so that the boulders would help support it. Using four ropes is also important in the installation.
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