Predicting Flooding to start the New Year with MICRODEM

 


This morning's tide prediction called for 3.1 feet above MLLW for 5 PM. (NOAA)


This is my tide model for the 5 roads most likely to flood.  It is created as follows:

  1. Get the 2017 county lidar survey.
  2. Create an NVS, non-vegetated surface, at 0.5 m and 1.0 m resolution, which will be in meters on NAVD88. The NVS removes the trees, but cars remain.
  3. Get the TIGER roads, and extract the 5 roads that control access.
  4. Interpolate the roads to 1 m spacing.
  5. Compute the elevation at each point on the road in the TIGER extract from the lidar NVS.
  6. Convert the elevations to feet, and adjust to MLLW with the offset for the tide gauge.
  7. Find the minimum elevation on each road.
  8. Get the OpenStreetMap data, and repeat the steps for the TIGER data.  The two data sets do not have exactly the same locations.

If the water reached 3.1 feet MLLW, all of these roads would be flooding or just starting to flood in the case of Bowyer Road.


The locations that would be flooding at 3.1 feet, with colors showing what would flood sooner.  #4 would just start flooding, but any waves would create problems on that road much sooner.  #3 has no path to the water, but could flood from the storm drains either failing to work or allowing bay water back into the drains.




The actual peak water level was only 2.71 feet.  (NOAA)




The predicted flooding at 2.71 feet was only two of the roads, and a quick field trip verified the flooding at those locations.


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