Yay New LIDAR!!

The end of last week came with a pleasant surprise of new 1.5m LIDAR being available for several counties in the Coastal Plain of Virginia. This meant I would be able to utilize the most current elevation data with the highest possible resolution. In my last post I explained how the 2m vs. 10m tests proved the 10m to be just as effective as the 2m and earlier this week I performed the same comparison using the new LIDAR. The results were very similar. A plot of the cumulative fraction drained along the field margin with both DEM resolutions showed the two to be matching exceptionally well. The higher resolution sets do allow for more accuracy in tracing the field margin, yet this doesn’t seem to cause a change in determining flow accumulation entering and exiting the field. This is great news! This allows me to analyze flow concentration on numerous fields as I am not restricted by the availability of high resolution data.

Also this week I worked with the rest of the team to practice more discharge measurements. We visited our reference stream in York River State Park and used the salt dilution method to determine the discharge through the channel at two transects. The method involves the input of a salt solution up stream and the measurement of conductivity changes downstream. Increased salts in water will increase the conductivity. Using a conductivity logger we can record the increase, peak and decrease in conductivity of the water. If we assume proper mixing in the channel, then the dilution of the salt-filled water can be determined and the discharge can be found with a few simple equations. We hope to use this method during the next storm which causes flow through the channel. Until then I will be analyzing fields throughout James City County with the 1.5m LIDAR and preparing the visit these fields in the near future.

Comments

  1. lkfunkhouser says:

    Not too hard. The DEM files are easy to find, it’s the manipulation of them that gets pretty sticky. The state park is very nice! You should go sometime!