WASCOBs siting and stream reach

[Elliott Kurtz]

Hello,

I am trying to understand the reasoning behind omitting WASCOBS that fall within 50 meters of the main stream reach. Is there more detailed documentation on why this criteria is included and where the 50m threshold comes from? Does the stream order matter or is it distance from any perennial flowing stream?

Thank You,

Elliott

[David James]

Hi Elliot

It is believed this was to prevent WASCOBS from being sited in the stream channel itself, within a floodplain, or within ravine type areas. In checking the code and this was changed to be 25 meters from the stream channel (rather than 50), as we believe people have asked about this in the past and sometimes WASCOBS are placed right above the "valley" of more upstream waterways. 

Stream order does not matter, but I would suggest placing a selection on the provided stream channel (either manually or selecting by stream order). Only those portions of the stream reach that are selected will be used to omit sites. 

I hope this helps

Dave JAmes

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[Elliott Kurtz]

Thank you for the information, this is very helpful.

Elliott

[Asell, Andy]

Dave can correct me if I'm wrong. But it most likely has to do with the last paragraph on page 71; 

"At each remaining point, a 100 m wide transect is drawn perpendicular to the mean direction of flow of that drainageway. The elevation profile of the transect line is then analyzed to estimate the shape of the drainageway and determine the suitability of the location for WASCOB installation."

Omitting any sites within 50 meters of perennial flow (i.e. half the length of a 100m transect lines) eliminates any possibility of a transect line spanning a perennial feature's cross section and erroneously considering it as a suitable site, assuming such a site somehow met all the other requirements. 

Andy Asell 

Environmental Specialist - GIS Analyst 

Water Quality Improvement Section

Department of Natural Resources

502 East 9th Street, Des Moines, Iowa 50319 

515-250-3303 (cell)

andy....@dnr.iowa.gov

www.iowadnr.gov

 

On Tue, Dec 5, 2023 at 3:02 PM Elliott Kurtz <eku...@chesapeakeconservancy.org> wrote:

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[David James]

Andy

Once again, reading the documentation proves to be a worthwhile effort... You are exactly right.

Dave

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