We've built a narrow dry stream to take seasonal rain from house to an edge of our large yard. At the edge the land slope drops pretty steeply and then joins up with a natural stream bed which then flows out to a big storm drainage bed. Trying to create 3 small mini "pond" bowls (2 to 4' wide) on the steep slope to slow down and hold water a few days for wildlife, like it does in the big storm drainage bed. "Built" the bowls with compacted claylike dirt, lined with underlayment cloth/rock, did a test run before cutting the expensive pond liner. Apparently when the rain came down hard during the night, it eroded the dirt under the cloth on the hill and filled all bowls up with dirt. The rain had also eroded the bowls around the rims and berms almost like a toilet flush! Does anyone have any suggestions?