building a lawnmower bridge

i mean, why not?

im getting settled into my new home and there is what looks like a drainage ditch on the side of the house, that empties into the pond

because of the snow melting and what not, it creates for a very soggy bedding
i would like to build a 8 foot bridge across this drainage ditch, that looks something like this and is strong enough to carry my small lawnmower

the wife would really like me to build the arch into it, just for looking nice

any thoughts, suggestions, advise you guys have?

bridge.jpg