Mapping Streambank Erosion

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Mapping Streambank Erosion2020-06-24T17:31:15-05:00
Unrated
Slight
Moderate
Severe
Very Severe
Riprap

Instructions:

  • Toggle between "River Left" and "River Right" using the buttons above
  • Hover over a point on the map for a photo of the selected river bank.
  • Click on a point on the map to view erosion information, view a larger photo, and skip to that location in the 360˚ video.

About the Streambank Inventory Project

Goal: Map and Inventory the Upper Iowa River Streambank within the Decorah city limits to analyze existing and future trends in bank erosion

Instructions: The data can be viewed on the map, in the 360˚ video, or as a photo of the river bank taken every 2-3 seconds. A larger screen is preferable. The time elapsed from the start of the paddle trip (HH:MM:SS) is used as a way to reference points in the data and video.

  • Toggle between “River Left” and “River Right” using the buttons on the map. The map, photo, and video should all update to show that side of the river.
  • Hover over a point on the map with a mouse for a preview photo of the selected river bank.
  • Click or tap a point on the map to view erosion information, view a larger photo, and skip to that location in the 360˚ video.

Partners: City of Decorah, Decorah Park & Rec, Winneshiek Soil & Water Conservation District, and Northeast Iowa RC&D.

Process: On March 31, 2020, Northeast Iowa RC&D team member Brad Crawford paddled the Upper Iowa River through the Decorah city limits with a GPS device and a 360˚video camera. The camera captured 30 frames per second in all directions, including images of both river banks. The camera’s GPS position was recorded every 2 or 3 seconds (5m accuracy), and these positions were then matched up to a single frame from the video showing the river-left and river-right bank (as viewed when looking downstream). The severity of bank erosion in each of the 3,732 images was then graded subjectively, using the following, generally-established criteria:

  • Slight. Some bare bank, but active erosion not readily apparent. Some rills, but no vegetative overhang. Maybe some exposed tree roots.
  • Moderate. Bank is predominantly bare with some rills and vegetative overhang. Some exposed tree roots but no slumps or slips.
  • Severe. Bank is bare with rills and severe vegetative overhang. Many exposed tree roots and some fallen trees and slumps or slips. Some changes in cultural features such as fence corners missing and realignment of roads or trails.
  • Very Severe. Bank is bare with gullies and severe vegetative overhang. Many fallen trees, drains and culverts eroding out and changes in cultural features as above. Massive slips or washouts common.
  • Unrated. No erosion, obstructed view, or another feature such as a stream inlet.

At two points the camera did not capture an image, and these images are shown as black frames. Streamflow at the USGS gage in Decorah at the time of filming was 924 cfs, a flow rate pushing the upper limit for being on the river in general, and especially while hauling a boatload of electronics!

Download the data:

Contact Information:

Northeast Iowa RC&D
brad@northeastiowarcd.org

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