Deerwood has worked with its partners to create a system of small-scale headwater retention structures within the upper reaches of three watersheds which drain an escarpment area of some 440 km² (170 square miles) in the Miami region. These "small dams" average approximately 20 acre feet in capacity, and are built in suitable areas on land offered by individual landowners. Between 1985 and 1995, 50 small headwater retention structures (small dams) were constructed, primarily on the upland tributaries of two waterways: the Graham and South Tobacco Creeks. A third drainage, the North Tobacco Creek, is relatively unmanaged.  

The Deerwood Association's 12 years of experience has been a learning process for them and their partners. In the first few years, numerous tasks were investigated and a number of dams were constructed. In this short time, it became apparent that a guideline was required to obtain reasonable estimates for optimum flood control. What type and size of dam would be most effective for its installation cost?  

In association with its main partner, the Prairie Farm Rehabilitation Administration of Agriculture Canada, this question resulted in a a general "small dam guideline" in which the dam would be designed to collect one inch of runoff from its upstream drainage area (watershed or catchment area). 
 

Pictured below is a culvert being installed for a backflood dam. The culvert is small and relatively inexpensive. The construction can be done with small equipment and manual labour.

Dam Design, Capacities, and Costs  

The following headwater storage structures typically define Deerwood's small dams:  

1) Dry Dam/Flood Control Structures serve to decrease peak flows during Spring runoff and Summer rainstorm events by retaining water for a short period of time, thus reducing flow rates. These structures are often incorporated into existing municipal roads (picture and map)  

2) Backflood Dams retain water at a shallow depth over large acreages of cropped or pastured lands. Water is retained for at least two weeks before being released in a controlled manner, thereby greatly increasing soil moisture (groundwater recharge) in the flooded area to the benefit of crops and wildlife (picture and map)  

3) Multi-Purpose Dams hold water for various seasonal, domestic, and irrigation uses. Each is designed to regulate seasonal storage, to control spring flood water, to release excess slowly, and to store water for summer use. Stockwatering, wildlife habitat, and fish rearing are other common uses. The dams are totally drained in the Fall to prepare for full flood control potential in the Spring. (picture and map)  

For a more detailed table of Small Dam sizes and costs by type of a structure, click on Dam Information Table.