Agren is an Iowa-based, family owned software start-up that has a unique business model based on LiDAR data. It is software as a service SaaS in that you buy a subscription to use their online conservation planning tools. This currently includes apps to design ponds, basins and wetlands, with more planned for release this year.
Agren aggregates the data on a state by state basis and they do warn that LiDAR data is not available in all locations, but as we know the availability is increasing. I assume that one of the key aspects of their service is that they develop the required digital terrain model to assist you in designing your project.
Its an interesting idea, with some obvious concerns about accuracy, liability and costs, but I think it is certainly worth a look.