Any work involving organic materials like soil, gravel, etc. are challenging because there are usually no straight lines and you often want to find volumes and areas. This is an area where photogrammetry (terrestrial or from a drone) and 3D laser scanning really shine.
The project shown here was one where we were asked how the water would flow down a road surface. We scanned the section of road and then wrote custom software to predict the paths of raindrops randomly falling on the surface. The multicolored lines in the image show the paths of many individual droplets.