I expect and hope the DNR desires calculations of watershed runoff flow amounts into your pond for historical large or heavy documented rain events in your region. That is just implementing good pre-planning and design. Watershed should be fairly easy to calculate with the aid of a USGS topographic map. The DNR may have on file the original plans and documents relating to design of the original pond. The sunshine law should give you a rights to view or receive copies of those documents. The original documents could save you some time and effort.
Erosion where there will be anticipated water movement is often controlled with concrete riprap. Broken concrete is often available free from concrete contractor's construction projects. You may need to draw down the pond's water level 5 to 8ft to accomplish whatever method you decide to use.
By impounding water you do have a responsibility to protect the receiving stream's integrity by having a sound dam and adequate oversized overflow structure / spillway.
IMO you need to do quite a bit more homework before deciding which plan is the best for you to use.
Last edited by Bill Cody; 03/25/14 07:23 PM.
