Dendritic flow patterns.
At the south end of Anderson Lake, a relatively permanent floodplain lake of the Illinois River system, is a seasonal body of water called Carlson Lake. In high water times, the excess water from Carlson flows over a spillway into Anderson, which sometimes floods over the lower roads of the camping and picnic areas of the park there. Later, when it is too low to have that outlet, Carlson recedes from evaporation, and as some of its waters flow to the lowest point of its lake bed, as shown here:
Super-Talumar f/1.8 55mm
Konica AR body to m42 lens adapter
Konica Auto-Reflex Full-frame/half-frame 35mm slr, set on half-frame
Kodak 100 Tmax
Here's a link to my post (including more examples) about shooting this roll of half-frame 35mm BW using a Takumar lens on a Konica body:
The HALF-FRAME-35mm Club - PentaxForums.com