Simple ways to save dams

One of the most common forms of erosion you encounter in the paddocks of Australian farms  is that around the farm dam. Its always nice to be able to help . The reason I posted this item is because,  yet again this old SCA design has solved yet another fairly simple but personally perplexing problem for a farmer . Instead of one of two outlets make 3 including a small economical PVC based pipe outlet .
How big should the pipe?   be they always ask.As if only one pipe is best . usually not as natural channel flows are flat and wide .  The  wonder of our work on farms was that pipe flows are simple compared to designing for surface and channel flows. The pipe through the wall only makes the hydraulic challenges on the flood bypass simpler-- in his case $1000 's of dollars simpler . For a conservationist its always good to leave a smile on the farmers face.