[EPIC] State-sourced DEMs for areas with quality issues in 3DEP

[CarsonPruitt-NOAA]

We've noticed very poor quality FIM in areas where the USGS 3DEP DEMs aren't derived from contemporary LiDAR. The "1/3 Arc-Second" areas indicated in the 3DEP Elevation Index map below are the areas that need better elevation data to improve the quality of FIM. The blue arrow (in Texas) identifies the location in the second figure that illustrates the significant drop in quality at the border of the 1/3 Arc-Second DEMs.

This is NRP FIM for the Sabine River near Gladewater, TX. The left-hand side of the map shows the low quality FIM derived from the 1/3 Arc-Second DEMs while the right-hand side shows FIMs derived from the 3DEP 1-meter DEMs. All FIM in this image is produced from 10m HAND.

I propose that we supplement 3DEP by sourcing LiDAR/DEMs from states and down-sampling to 10m to match the our current HAND resolution. We'll have to change our current setup to allow for DEMs from multiple sources and test the possible edge effects of using non-continuous DEMs. Additionally, our team will need to screen the alternate DEMs for hydro-processing (bridge removal) and down-sample them to 10m prior to integration.

We have confirmed that the lower quality 3DEP data has the same effect in other states that have state-wide LiDAR programs such as Kentucky, Oregon, and Washington.

[CarsonPruitt-NOAA]

The Finger Lakes region of NY also seems to be pretty poor quality even though its within the 1m section of 3DEP.

[RobHanna-NOAA]

new 10m 3Dep's coming soon. Almost done.