In edge-of-field / runoff monitoring sites it is not uncommon to have flow running in ill-defined channels (versus creeks or small streams).  The problem then becomes how to capture and direct the flow into a flume or weir to quantify and measure the flow.  Here wing walls are a good solution.

Wing walls are nothing more than flat walls that extend upstream from the flume or weir pool and which serve to direct the flow into a defined channel. 

So long as the walls are watertight, the material of construction is not important.  Plywood, galvanized sheet, railroad timbers, and formed fiberglass walls all work well.  Just make sure that flow cannot bypass or scour under/around the wing walls.

Image:  University of Arkansas - Big Creek Research Extension