There is a very important distinction between a Cattle Grid and a Catch Pit.
Cattle Grids are designed to contain stock and so to miniseries the harm if an animal become trapped in it
Catch Pits look like cattle grids but are designed to capture flood water, running along a road or drive. They should never be used to contain stock as animals could be injured, potentially fatally, by becoming trapped with their legs in the pit.
Catch Pits are usually shorter in length along the road but much deeper to contain the maximum flows. Depths can exceed the length of an amimal’s leg !