I would create a ditch via landscaping. You can fill it with weeds and rocks for effect. On my region Birch Grove Spring I have some storm drains I made. Some have a BC salmon painted on the asphault in front of them but you can take that piece off. I also have some road tunnel enders/fakers that could be modified easily into culverts. But I think R. Lion might have some stuff like that too. hop://watersplash.inworldz.net:8002/iPleasure/299/1004/197...
I send 2 objects in OsGrid to you.... One of em is only texture, but include Normal Maps which is nice.... If it is not what you are looking for: maybe send me URL of a picture. Enjoy :-)
send me the UUID of your avi, that I can find you in Hypergrid.
P.S. no answer yet.... you can find your UUID: right click to your own avi-->Profile-->first TAB, second line-->KEY