Lidar map of some of the terraces I have been exploring along the Potomac River in Washington. You can see some of the complex flood chutes, terrace remnants and so on I mentioned. The flat blue is the river. The bands of color toward the bottom are the bluffs; the terrace is in aqua, with shading to indicate relief. Detail below.
This dataset actually comes from FEMA, so it is probably part of their plan to seize control of the country on Obama's "last" day in office. But meanwhile it can serve my archaeological purposes.