A few more thoughts about the situation in general.

I think the creek dams will always leak to some extent. But mostly, the dam will hold more than the leak creating a "full" pool except in very dry situations.

My dam has zero chance of ever sealing with what knowledge I have at this point in time.

I recently walked a property that had a creek on it. The creek ranged from 10-20' in width. They had a series of small dams creating pools. The method of dam they used resembled a cable foot bridge (planks held together with two cables), which at first was placed across the creek perpendicular to the creek bottom, and eventually leaned over down stream. After time, a lot of small rock and silt had built up against the dam on the upsteam side. There was overlap in the planks.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."