That vegetation provides impediments to those water currents, resulting in a 'funneling' or 'channeling' of the flow. ANY mass in the area of moving water is an obstruction to that flow and the water will break around the obstruction. Moving water diverted from its natural path also creates eddies in the vicinity of the obstruction. Fish LOVE eddies because they are good energy-efficient holding areas. Moving water carries plankton and other small aquatic life, which are the food staples of the small fishes.
Small fish gather on the flow to feed.
Bigger predators gather on the flow to feed of the small fish. There are also a few active water-level control gates that feed into the Farm 13 side, as well as one near the boat ramp area. Nuff said on moving water. There is a big difference between 'structure' and 'cover'. Cover is a concealment item, both for predators and prey.