Hey guys! I saw a random YouTube video about beaver making dams and I thought I would share some of the incident with you guys! J

BEAVER DAM: As the name speaks, it?s simply a dam made by beavers. Generally, its? made on a clay water-bed. And these dams are very important to the nearby eco-system. The whole nearby eco-system is somehow affected by the beaver dam. That?s why they are called ?Key stone? species.

Construction:  Beavers prefer to build their permanent dams on a clay-type soil. Clay can be packed with the woody material, leaves and grasses to hold a dam together. Gravely or sandy soils can't be packed to hold water.  
Beavers have good reason for building their permanent dams on a clay bottom. When the beaver uses sticks, poles, limbs or other woody material, the heavy end of this wood is placed on the dam and the smaller ends are on the lower side of the dam. On the heavy end there is usually some heavy mud packed on it to help hold it in place. When the water is high and there is force against the upper side of the dam, the smaller ends of the poles and limbs dig into the bottom on the lower side of the dam and help hold the dam in place:  If the bottom is solid stone or shale, the water pressure behind the dam during periods of high water will push the dam off its foundation.
 If the bottom under the dam is gravely or mostly sand, the turbulent high water will erode the foundation from under the dam construction. By selecting a clay bottom, beavers can be sure of a strong dam.
It is on the upper side or deep water side of the dam where the animal digs the clay for the dam construction or repair. This removal of mud and clay also deepens the water close to the dam.

Eco-benefits:  These dams are very important and of great use to the surrounding environments. The importances of these dams are manifold. They are simply given bellow:

Restoring Wetland: Dam building can be very beneficial in restoring wetlands. Such wetland benefits include flood control downstream, biodiversity (by providing habitat for many rare as well as common species), and water cleansing, both by the breakdown of toxins such as pesticides and the retention of silt by beaver dams. Over the eons, this collection of silt produces the rich bottom land so sought after by farmers. Beaver dams reduce erosion as well as decrease the turbidity that is a limiting factor for much aquatic life.

Flood control: A beaver dam has a certain amount of freeboard above the water level. When heavy rains occur, the river or lake fills up and the dam gradually releases the extra stored water. Often this is all that is necessary to reduce the height of the flood wave moving down the river, and will reduce or eliminate damage to human structures.

Pesticide removal: Agriculture also introduces pesticides into streams. Some of these toxicants are metabolized and decomposed by the bacteria in the cellulose-rich bottom of a beaver dam.

Home for salmon and trout: There are several reasons why beaver dams increase salmon runs. They produce ponds that are deep enough for juvenile salmon to hide from predatory wading birds. They trap nutrients in their ecology and notably the huge nutrient pulse represented by the migration of the adult salmon upstream. These nutrients help feed the juveniles after the yolk sac has been digested. They dams provide calm water which means that the young salmon can use energy for growth rather than for fighting currents larger spaces with a food reserve have a better rate of survival when they reach the sea. Finally, beaver dams keep the water clear which favors all other fishes too.

The dark side: Beaver dams can be disruptive the flooding can cause extensive property damage, and when the flooding occurs next to a railroad roadbed, it can cause derailments by washing-out the tracks, or when a beaver dam bursts and the resulting flash flood overwhelms a culvert. Traditional solutions to beaver problems have been focused on the trapping and removal of all the beavers in the area.

Source: Wikipedia Article

Google earth image of the largest beaver dam in the world in Canada.