<p>Illustration of movable dams.
From chapter 7,  page 7-6 of a Corps of Engineers engineering pamphlet.
</p>
(designated on website as "ep1110-2-14")
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/70020260@N04">William Alden</a> from Louisville, Kentucky, USA
CC BY-SA 2.0
<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/bill_alden/6791988641/">99c091 supplement 1: movable dams diagram (1952)</a>