So this may not be considered a 3rd party add-on since Autodesk just acquired it on May 11, 2020, but this tool is going to be freaking awesome! This is not a new tool to the market, this came from 3AM Solutions and has matured into a great addition to the software. I’m sure you’ll being seeing more info from Autodesk soon, but I wanted to get this on your radar as something to look forward to.
River and Flood Analysis
Also not a 3rd party, but the River and Flood Analysis tool is an often overlooked piece of software that the majority of you already own. This is a river modeling software package that supports HEC-RAS within the Autodesk Civil 3D environment. The Autodesk River & Flood Analysis module makes it easier than ever before to compute water surface profiles for modeling rivers, bridges, culverts, spillways, levees, floodplain and floodway delineations, stream diversions, channel improvements, and split flows.
To learn more about Civil 3D add-ons, click here.