Q.Will cattails be detrimental to a drainage ditch
We have cattails growing in the ditch behind our house and this ditch is there for drainage of bay water during high tide and hurricanes. Should they be removed?
It's true that if cattails' growth gets thick, they can impede flow of water through the drainage ditch. They probably should be thinned if not completely removed. You can contact the county extension service for advice on practical solutions for your area. This article will help you locate the nearest one: https://www.gardeningknowhow.com/garden-how-to/info/what-is-extension-service.htm
This article has some general information on cattails that you might be interested in: https://www.gardeningknowhow.com/ornamental/water-plants/cattails/controlling-cattails.htm