Tag: BDA

Topographic Survey Shows Progress at Triple Creek

OHA partners with US Fish and Wildlife Service to conduct topographic surveys of the stream channel and banks to measure (even small) changes in elevation of the creek bed and shifts in the streambanks over time. The topographic surveys show how silt, sand, and gravels have accumulated, scoured, and moved throughout the project reach as the force of water carries the sediment downstream, recruits it from the streambanks, and deposits it on the creek bed. 

Graph above shows topographic survey (elevation data) plotted versus the relative distance in the thalweg of the stream. Points A-D on the graph are comparable to those points on the map below.
Aerial view (above) of Triple Creek Project area. Cooler colors signify aggradation and warmer colors signify erosion. Both processes are critical to the restoration of this stream and wetland.
The aerial view above shows that the reach is significantly longer and more sinuous now than it was before the project started.

Progress By The Numbers: 

  • 3800 yd3 = 271 dump trucks of sediment deposited in the reach!
  • 1500 yd3 = 107 dump trucks of sediment eroded in the reach!
  • 5300 yd3 = 378 dump trucks of sediment shifted within the reach!
  • 2300 yd3 = 164 dump trucks of sediment carried from outside the project area and deposited in the reach!

BDAs at High Water

Beaver Dam Analogue (BDA) #8 was installed up against the incised banks of Myers Creek. During high water of spring 2017, the stream pushed its force around the BDA and into the bank, widening and lengthening the channel as needed. This sediment was then carried downstream, where it was captured by other BDAs and settled on the streambed. As a result, the streambed is now closer to its floodplain!

The ultimate goal of this project is to reconnect the stream with its floodplain, and foster the ecological benefits associated with that connection. The following video is taken at the upstream end of the structures that our team installed in the summer of 2016.

Below you can see that large wood is changing the movement of the stream, causing it to spill out over its banks and inundate the floodplain in a broad area on both sides of the creek. This is the least incised portion of the project area, and thus the first to reconnect. It is very exciting to see this degree of success during the first high flows after in-stream construction.

Change Over Time: BDA 9

Left to right: summer 2016, initial construction; spring 2017, first high water; summer 2017, adaptive management construction; spring 2018, second high water

Click to enlarge

Change Over Time: BDA 14

Before, during, and after construction–the streambed is raised four feet higher in one year!

Click to enlarge
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