I mentioned earlier the removal of a "rubber dam." This is one of a series of diversion dams on Alameda Creek that consists of a concrete foundation and an inflatable rubber section to hold back water. As part of a fishery-restoration project, the Alameda County Water district is decommissioning the dam, removing the inflatable section, and cutting a notch in the middle of the concrete structure to allow fish to pass through at low flow times. Read more here if you're interested.. My walk around Quarry Lakes takes me by that dam. The walking path has been diverted away from the main trail while they work on the dam. The rubber section has been removed, but the water continues to flow over the concrete foundation. While I walked the path tonight, I saw in the deepening twilight a mother duck and three ducklings making their way down the pond formed by the dam's foundation. They hopped up onto the foundation and continued to float down the flat top of the dam. At the downstream end there is a concrete slope down to the stream bed below.
I wondered what the ducks were going to do. Just before the lip of the spillway, the three ducklings, which had been preceding their mother downstream, backpeddled furiously. Their mother went over the edge and not very gracefully landed in the pool below, flapping and squawking. The ducklings paddled over to the shore, clambered out of the water, and portaged around the spillway, rejoining their mother below.
This is the opposite of how I'd expect a human family to behave. If it were a mother with three kids in boats, the mother would say, "Now children, let's climb out and carry our boats down below the dam," while the children would say, "But mom, we want to go down the water-slide!"