Electronic
Memo (email) from Scott Downie, CDFG NCWAP Lead
----- Original Message -----
From: "Scott Downie" <sdownie@dfg.ca.gov
To: <cathy@ceres.ca.gov; "Cynthia LeDoux-Bloom" <CLedoux@dfg.ca.gov;
"Steve Cannata" <SCANNATA@dfg.ca.gov; <reedy@humboldt1.com
Cc: "Barry Collins" <bcollins@dfg.ca.gov; "Gary Flosi" <GFLOSI@dfg.ca.gov;
"Gary Stacey" <GStacey@dfg.ca.gov; "Kevin Hunting" <KHUNTING@dfg.ca.gov
Sent:
Subject: stream order, ad nauseum
If you-all have not had enough discussion about the variations of determining stream order, please check out the discussion in Leopold's A View of the River, Stream Network section. He discusses the differences between, and the limitations of both the Horton and Strahler schemes of
naming stream orders. He mentions some research and ideas of his that might help in resolving such earth-shaking questions as at what point does the reduction of flow determine the difference between perennial and intermittent streams and how do we translate that to a USGS map?
Interestingly, he kind of pensively gives up when he learns that the "blue lines on a map are drawn by nonprofessional, low-salaried personnel. In actual fact, they are drawn to fit a rather personalized aesthetic" (pg. 228).
Considering this, among other things, many years ago when developing our DFG Restoration Manual, we decided that for the needs of our investigations of North Coast (at that time) anadromous fish conditions and status, that adhering to the courser Strahler method and solid blue lines on 1:24,000 USGS topos would suffice, reduce inconsistent staff interpretations of the perennial, intermittent, and ephemeral flow conditions, and simplify training complexity. We remain satisfied with that determination.
In the KRIS Gualala, the IFR folks have chosen to use something more akin to the Horton scheme which goes well above the solid blue lines and thus changes the stream order considerably. In looking at the Gualala KRIS, and comparing their stream order determinations to our Tributary
Reports' stream order determinations, we find they are certainly not compatible. For example, DFG first order streams are either second or third order streams according to the IFR scheme. The same problem extends downstream, of course. Rockpile, an IFR fourth order stream is a third order stream in the DFG scheme.
Unfortunately, in my comparitive investigation I have found that there is inconsistency in the variance and a simple cross-walk table will not work. Therefore, this fundamental inconsistency needs to be acknowledged in the KRIS product since it leads to further inconsistent analysis of habitat parameters like pool depth, etc. There is no right or wrong on this issue, but it would seem to be a bit easier on the audience shared by NCWAP and KRIS if we could achieve conformity.
DFG has no plans or need, based upon our analysis, to revisit our thousands of Tributary Reports and revise them to the Horton scheme, nor are we willing to make changes in one watershed (the Gualala, in this case), and make it inconsistent with all the others we have reported upon. We are happy to share our products for incorporation into KRIS. If you do not have our stream order data (it can be found on the first page of each of our Tributary Reports in the Watershed Overview
section), we will provide it promptly. In any event, if you retain the current stream order designations, we would like to request the variance be explained in the KRIS product. Hope this helps and can lead to better, more consistent and useful products from both NCWAP and IFR.
Gary R., I would appreciate you sharing these thoughts with your IFR staff; I do not have their addresses since my last computer crash.
Thanks.
Sd