Trash racks and debris cages are used to prevent floating debris from clogging stormwater outlet control structures. The goal is to trap material on the outside of the structure where it can be easily removed. Failure to keep a riser structure clean can greatly diminish the flow capacity possibly resulting in overtopping of the embankment.

A trash rack will collect this debris in plain sight which will encourage maintenance as needed, as opposed to debris collecting unseen inside a structure with no apparent problem until the structure becomes completely clogged.