Mr. Pat Higgins
KRIS Project Field Coordinator
Institute for Fisheries Resources
7981
Arcata
Dear Mr. Higgins,
The
California Geological Survey (CGS) has completed its review of the Klamath
River Information System (KRIS) Gualala website. CGS previously reviewed and provided comments
on the KRIS Gualala CD in a letter dated
A
major concern with the KRIS Gualala website is the divergence between the KRIS
web site and the North Coast Watershed Assessment Program (NCWAP) Gualala River
Assessment Report, dated
This discrepancy has large implications for future land management decisions and it will be difficult for the Gualala Watershed stakeholders to formulate land use policy and practice if this ambiguity is not resolved. The KRIS Gualala was developed under contract with the California Department of Forestry and Fire Protection (CDF) as part of the NCWAP deliverables. Therefore, it would seem that the website should match the findings of the NCWAP team, of which the Institute for Fisheries Resources (IFR) is a partner, as stated in the program description of the Report. Furthermore, it is CGS’s understanding that the purpose of the KRIS Gualala website is to provide another avenue to present the scientifically based findings of the NCWAP assessment. If this is the case, the KRIS Gualala website should be in agreement and compatible with the NCWAP findings rather than presenting information and conclusions that are not supported by the most complete set of data.
Previous
CGS comments on the KRIS Gualala database were
recorded in a letter from Mr. Steve Sterling to Mr. Patrick Higgins dated
The Technical Support Document (TSD) [prepared by the
The TSD Plate 4 is a geologic map indicating different
terrain.
The response does not address the comment nor address the
issue. The geology across the watershed
varies and should be reflected on the KRIS Gualala website. It has been agreed that the NCWAP assessment
has provided more data than what was available to the NCRWQCB during
development of the Gualala TMDL. The
geology in the watershed is more accurately represented by the CGS maps and
should be used in the KRIS Gualala website.
If the geologic map used in the TSD is included on the website, a
qualifying statement must be added that indicates the assumption that the
geology across the watershed is not similar and the newly completed CGS maps
are more complete. In addition, the
licensed geologist responsible for preparing the TSD geologic map should be
identified.
The TSD does not include mapping deep-seated landslides
for development of the total maximum daily load (TMDL), which as a result,
overlooks a potential major sediment source.
The TSD identified and estimated sediment from the active portions of large, deep-seated slides, although they did not map the larger non-contributing portions of these features.
This is not our
understanding and this response is misleading. CGS staff has discussed the
development of the TMDL with NCRWQCB staff.
Review of the TSD and discussions with NCRWQCB staff confirmed that the
TMDL underestimated the area of deep-seated landslides. The TSD assumed 10 percent of the Franciscan
Central Belt formation were earthflows and mapped only shallow point slides
throughout the watershed. Additionally, the NCRWQCB used the rate of 1.6
mm/year for non-earthflows and 48 mm/yr for earthflows to develop the
TMDL.
CGS’s findings
identified active and dormant deep-seated landslides (earthflows, rock slides
and composite slides) cover approximately 40 percent of the entire watershed,
which indicates the total area of natural mass-wasting is notably underestimated
in the TMDL. Sediment rates from
published literature for soil creep, uplift, earthflows and other mass wasting
range from 300 mm to over 15 meters per year.
The NCRWQCB’s underestimation of deep-seated
landslides and the use of rates less than most published values results in
underestimation of natural mass wasting by approximately an order of magnitude
or more.
The landslide mapping for the TMDL study was not
performed by a
One needs an engineering
geologist's license when rendering site-specific land use advice in
An
inquiry to the
Similar charts and discussion regarding sediment sources
and their purported volumes of derived sediment have been removed from the
Gualala Synthesis Report with consensus of all Gualala Team members.
The information stands
as the best available for the Gualala, although CGS’s questions regarding TSD
help understand the limits of its use. KRIS is science driven, not consensus
driven.
KRIS
relies on the TSD as best available and does not acknowledge that there is more
data available from CGS efforts. CGS
data and conclusions are based on evaluating deep-seated as well as shallow
landslides, historically active as well as dormant landslides, which provides a
more complete picture of mass wasting in the watershed. Based on the more complete evaluations, CGS’s
conclusions deviate significantly from the conclusions in the Gualala
TSD/TMDL. CGS maps and final geologic
report (an appendix to the NCWAP assessment report) will be finalized with the
NCWAP Gualala assessment report and available
TMDL charts
should be removed from the KRIS Gualala CD or there should be a description of
the limitations.
Reservations and qualifications offered by the CGS will be used in all
captions or background pages where TSD data is discussed.
The KRIS Gualala should include the limitations of the TSD data and
conclusions to provide a more complete picture of the data set. The assumptions used including the geology
and hydrology are homogenous across the watershed and that only
shallow land slides were mapped should be included.
It is recommended that the CGS relative landslide
potential maps be incorporated into the KRIS Gualala CD (replacing the SHALSTAB
maps) when they are completed.
Please supply electronic
data and model parameters.
Maps and meta data will be provided when maps are finalized in
October 2002.
Specifically, how has
model run been changed from a standard Dietrich et al. (1998) model? Layers
will be added to KRIS Gualala Map project but SHLSTAB will be retained because
it is scientifically valid and useful.
CGS does not agree
with the statement. Comments regarding SHALSTAB
modeling from Technical Advisory Committee (TAC) on Forest Geology from the
State Mining and Geology Board were provided with the March 15, 2002 comments.
Added
CGS disclaimer on SHALSTAB to Background page.
The disclaimer should
include a copy of the TAC comments.
SHALSTAB was used as a quality control check as well as other models in
developing the relative landslide potential map. SHALSTAB is based on slope and convergence
using the DEMs. It does not consider the
geologic formation or address deep-seated landslides, which are significant
factors in slope stability.
KRIS products should not be released until the CGS relative landslide potential maps are incorporated in the final KRIS products.
KRIS Gualala can add the
CGS data as it becomes available. What
is the release date for the data?
CGS will release maps
in time to be incorporated into the final Gualala report due on October 1,
2002.
“The parameter poor, topography-based SHALSTAB program falls well below the current standards of geologic/geotechnical practice.”
It does not meet
standards for site-specific land use decisions but serves well for risk
assessment and as a reconnaissance tool at a watershed scale, which is how it
is used in KRIS.
This is not
correct. SHALSTAB misses several areas
in the
If the KRIS data base is released in its current form with out including the limitations regarding SHALSTAB and the recent CGS sediment calculations, the opportunity for geologic data and conclusions to be misconstrued and misused by community members, watershed stakeholders, and local and regional agencies is greatly increased.
Policy
question. Can’t we trust the public (and other
agencies) to participate in an informed dialog?
Presenting incomplete
information and not including the limitations of existing data and conclusions
(e.g. TMDL, TSD and SHALSTAB) does not provide the public with a complete
foundation to make informed decisions.
Providing only part of the information is not scientifically based and
can be misleading and biased.
In the spirit of completeness and providing available data and conclusions to the public, CGS requests that the new maps, geologic report and associated data compiled and developed under NCWAP be incorporated in the KRIS Gualala website. Even though there are differing conclusions, additional information and data will broaden the baseline information and can enhance the decision-making ability in regard to land management activities.
If you have any questions or comments please contact me at 916-322-2588.
Stephen C. Sterling, CEG
Supervising Geologist