GW,
Both of the two ponds nearest me, stock catfish and tilapia, neither have aquatic weed problems. The difference in levels is about 1 meter, about the distance of water level drop during the hot season.
These ponds are dug from fairly flat ground and the top of the lower level is usually the existing ground level, the higher level is created with the dug out material, set back from the top of the lower level about a meter and about a meter high. No keyway is dug. Many times the inside and top surface of the upper level are covered with a clay/rock mixture which, while ugly, inhibits weed growth and deters erosion. It is easy to walk on and wicks the water to the underlying clay, eliminating almost all of the mud that would be encountered without the clay/rock.
There is only one overflow and that is in the top level.
Of the hundreds of ponds near me, almost none are attractive, looks is not an objective here. There is one pond, about an acre when full, where the owner has taken pains to see the that the ground cover follows the water level. It is some type of low growing grass that requires cutting only once or twice a year. It looks nice and greatly reduces erosion. The water level drops about twice the distance of most ponds and without the grass would look terrible.
The most attractive ponds are usually the naturally occurring ones that have few if any fish. The weeds/plants grow along the banks and follow the water level, few of these ponds become overgrown, since we get quite a bit of rain the weeds/plants are almost always green.
An aside, one of my neighbors has ducks and geese and no herons.
