In this movie, you adjust the sloped surfaces to cap the gaps by placing custom walls.

Using 3ds Max Design with Civil 3D - Part 21

The official learning channel for Autodesk® 3ds Max® software, a comprehensive 3D modeling, animation, rendering, and compositing solution for games, film, and motion graphics artists. The Autodesk® 3ds Max® Learning Channel provides tutorials of all levels to help you learn Autodesk® 3ds Max®.