Select a flat area on that map, use the terrain down tool, and click two times. After that, use the level terrain tool and make a line 2 x 8 squares. Next, use the create surface water tool and fill the line to make a creek. Make a bridge over the creek. Next, choose the place pipe line tool but do not make pipe. Finally, select the level terrain tool and level the terrain under your creek when underground. Go aboveground and you will see that you have a bridge over the ground.