You can also use the topo to determine how much soil will need to be moved to create the dam. Now this is not going to be an exact figure you will need to shoot grade, determine soil types etc, but it will give you a pretty good idea up front of the yardage involved in your early planning and site selection. Example: Most topo's online if not all are based on 10 ft elevations. You can scale the distance across the area you are considering for the dam. Once you have the length determine the cross section of the dam based on the elevations. Once you determine the width of the top of the dam and the side slopes on front and back you take the area of the cross section and multiply it by the length. Then carve out or subtract out the elevation slopes on each side of the valley. You will have a pretty accurate figure on how much dirt will need to be excavated. You can also add in the core trench to the figure to make it even closer.
