What has me wondering is I nearly always see the bottom of a pipe inlet or outlet armored with rock (apron as I call it) and then only sometimes see up the sides and on top of the culvert armored. This is in agricultural drainage work, commercial developments, drive culverts, and road projects.


Culverts may be designed to operate submerged and sometimes, you can get fasting moving water and almost a sucking at the entrances, it makes sense to armor all around in those instances. On outlets are folks at times just requiring the apron to be armored, not up the side slopes and over the top of the culvert? On most outlet flows I see it as a good thing to have, but when I really think about it I cannot see a reason to have it other than it gives me some extra feel good.