LiDAR data is freely available on the Internet, but good luck trying to get it into Civil 3D. The two most popular formats, from my observations, are LAZ and zLAS. LAZ is a compressed LAS, but that format is open-source, so Autodesk should include it. As things stand right now, you have to use LAStools to uncompress a LAZ. zLAS is an ESRI proprietary format. ESRI has a free "tool" for unlocking it to LAS.
Except for Tiff's, I've not run across ANY of these other supported file formats:


Dave