Retrofitting farm dams and vastly increase wildlife habitat and productive edge function, while accessing the material/earth to repair the dam wall on-site and/or increase the freeboard of the dam wall for its safety and the safety of your neighbours below the dam.
My Process
The first thing I look for in a dam retrofit other than the spillway, is the freeboard [dam wall above spillway height] very often it's not much and for the safety of the dam.
Free board is critical.
Then I'm looking at the batters of the dam wall inside and outside, what degree slope are they, can you build the dam wall any higher? as you go up you've got to go out to keep the batter grade reasonable, we can than get a idea of how high we can raise the wall if any.
Once we work out our desired new height of the top of the dam wall, we then come down to our spillway height which gives the dam wall its freeboard and new water level, transferring this height around the dam's edge gives you a height of where the new water level will be.
Form this process we get an idea of how much material in cubic metres we need to excavate to repair the dam wall give it a freeboard, I call it the insurance policy that builds natural capital by increasing habitat and productive edge.
My general approach to Dam retrofitting is to cut a bench in one side of dam edge ideally closest to the dam wall as possible or sometimes on both sides, its all about logistics of time and energy to move the material into position, this decision also depends on the topography/slope above the high watermark of the dam edge.
This high water mark gives us a measurement to work from for our bench excavation, so we can either cut the bench so it's under the water or we cut the bench so it's above the water or both
which opens up the opportunity of putting in a productive crop on the Waters Edge or creating the human Sanctuary a place to sit comfortably and observe or just chill by the water's edge.
We can also utilise fallen trees, stumps or large rocks to position around or in the dam for extra habitat
There also the classic edge effect you can install like chinampa effect you can see in the video below from Green Cauldron Farm
There are so many opportunities for retrofitting existing dams for many reasons, in Australia Land-care gives grants to fence off farm dams and install water troughs for livestock for wildlife habitat and the live stock get better water quality a win win situation.