The Cache Creek Improvement Program (CCIP) requires that the Cache Creek Technical Advisory Committee (TAC) produce an annual status report in January of each year for the Yolo County Board of Supervisors. The 2017 Annual Report was slightly delayed this year due to the sustained high flows in Cache Creek. The flows triggered the need for updated aerial and topographical data. This data is used to document physical change in the Creek and feeds into various hydrologic and hydraulic models.
This annual report provides a record of the implementation of the Cache Creek Resources Management Plan (CCRMP) and CCIP for the 2017 Water Year, which spans the period of October 1, 2016 to September 30, 2017.
It is intended to: 1) document the previous year's monitoring results, field observations and any completed in-channel restoration or stabilization projects; 2) provide analysis of data and trends; and 3) identify recommendations and projects for the next year. This report represents a critical component of the adaptive management of lower Cache Creek.
Background
The Cache Creek Area Plan (CCAP) was completed in 1996. The CCAP is comprised of the Off Channel Mining Plan (OCMP) and the Cache Creek Resources Management Plan (CCRMP). The goals of the CCAP effort are protection of groundwater, preservation of agriculture, restoration of Cache Creek, and regulation of commercial mining. Implementation of the CCRMP is discussed further below.
The CCRMP (adopted August 20, 1996, and amended August 15, 2002) is a creek management plan. It eliminated in-channel commercial mining and established an improvement program for implementing on-going projects to improve channel stability and restore habitat along the creek banks. The CCRMP provides a policy framework for the restoration of 14.5 miles of lower Cache Creek and includes specific implementation standards. The Cache Creek Improvement Program (CCIP) is the implementation plan for the CCRMP and identifies specific categories of projects that include: bank stabilization, channel maintenance, re-vegetation and habitat restoration.
The CCIP is overseen by a Technical Advisory Committee (TAC) comprised of three scientists charged with advising the County on implementation of in-channel restoration and stabilization projects. The work of the TAC is, by design, an iterative process driven by on-going monitoring and technical feedback on creek performance. The TAC is comprised of a fluvial geomorphologist, a hydraulic engineer and a riparian biologist.
In January of each year the TAC is required to prepare, and present to the Board of Supervisors, an annual status report for their activities of the previous year. This report fulfills that obligation and provides an opportunity for the TAC, community, and stakeholders to step back and take a larger perspective in looking at both the creek and the CCRMP with a critical eye for improvement.
Program Accomplishments
In November 2016, the second year of the required five years of mercury sampling in off-channel mining wet pits (Section 10-5.517, OCMP) was conducted, utilizing the services of Dr. Darrel Slotton. The Year #3 sampling event is scheduled to take place in November 2017. The report for the first year (2015) was published on the Natural Resources webpage in May 2017 and is attached as Appendix C of the Annual Report. County staff is currently reviewing the draft report for year two (2016) mercury monitoring.
There was one surface water quality sampling event this water year, which occurred on December 16, 2016. The samples from this event were analyzed for a suite of water quality constituents. A detailed discussion of these results is included in Chapter 3 of the Annual Report.
Three public Cache Creek Technical Advisory Committee (TAC) meetings were held during Water Year 2017: April 20, 2017, June 13, 2017, and August 22, 2017. These meetings were attended by TAC members, County staff, members of various partner agencies, program stakeholders, and the public.
On March 7, 2017, the Yolo County Board of Supervisors approved the repeal of the sunset date of County’s nighttime OHV ban ordinance. In January 2016, the Board of Supervisors approved an ordinance banning the use of off-highway vehicles (OHVs) in Cache Creek between the hours of 7:00 p.m. and 6:00 a.m. This ordinance was set to expire on February 15, 2017 if the one-year sunset date was not repealed. More information on the ordinance and its related components can be found in Section 7.2.4 of the Annual Report.
On March 17, 2017, the Natural Resources Division released the “2017 Technical Studies and 20-Year Retrospective for the Cache Creek Area Plan.” This report was prepared by the three TAC members and contains three individual reports, one specific to each of the three CCAP scientific disciplinary areas – fluvial geomorphology, hydrology and water quality and biological resources. This report was the result of an extensive technical analysis of collected data, other available information and analysis and conditions within the creek and is a key component of driving the proposed draft edits in the CCAP 20-Year Update. The 2017 Technical Studies provide an update to the 1995 Technical Studies. Appendix D in the Annual Report includes a web link that takes you to the online version of the 2017 Technical Studies.
On May 8, 2017, the Natural Resources Division released draft proposed updates to the Cache Creek Area Plan as a part of the CCAP 20-Year Update. The purpose of this update is to analyze trends and adjust the program to avoid unexpected effects on resources management, particularly focusing on changes in creek conditions that have occurred over the prior 20 years; analysis of collected data from monitoring programs, habitat restoration, channel stabilization, and reclamation efforts; and the existence of any new regulatory requirements. The CCAP 20-Year Update is anticipated to be completed by mid-2018.
The TAC conducted its 2017 Creek Walk on July 12-14, 2017. The Creek Walk is the annual physical inspection of the creek with the main purpose of documenting channel conditions, as required by the CCIP. The entire length of the CCRMP boundary is covered over the three days. Joining the TAC on this year’s Creek Walk was County staff, representatives from the gravel mining industry, program stakeholders, and members of the public. TAC observations from the 2017 Creek Walk are provided as Appendix E of the Annual Report.
On July 31, 2017, the County released the Draft Cache Creek Area Plan Parkway Plan and Draft Feasibility Study for public review. The Parkway Plan provides a vision and integrated management plan for open space properties the County already owns, or will receive title to, as a result of the long-term partnership with the local aggregate mining industry. The Draft Parkway Plan, which was produced by Callander Associates and Tschudin Consulting Group, provides draft guidelines and specifications for development, access, use and management of each property, including the development of a trail system and public access. The accompanying Draft Feasibility Study, which was produced by BAE Urban Economics, analyzes the financial feasibility of various levels of parkway development, by identifying operations and maintenance and capital improvement costs of each property, along with potential revenues generated by public usage. Both documents can be accessed here:
In September 2017, Towill Inc. conducted an aerial survey for the Lower Cache Creek area. This survey included the simultaneous capture of LiDAR and high-resolution aerial imagery. The data obtained from this survey was instrumental in the production of this annual report.
In October 2017, the Natural Resources Division released the Cache Creek Area Plan Dashboard website. This site provides real-time access to the primary data used by the Cache Creek TAC, the County, mining companies and other stakeholders. The data included on the site is important to the implementation of the Cache Creek Area Plan. Access to the data is organized in the form of a data “dashboard” that displays key information over time related to water resources, geomorphology, and vegetation and wildlife. New data will be uploaded to the site after the adoption of each Cache Creek Annual Status Report. The website was designed and created by the TAC Geomorphologist and TAC Hydraulic Engineer and can be accessed at the following link:
The County’s Manager of Natural Resources continues to serve as the Chair of the Water Resources Association (WRA) of Yolo County’s Technical Committee and was made Chair of the Westside Coordinating Committee for a two-year term, highlighting this program’s value in providing watershed monitoring and protection.
Summary of Significant Findings
Hydrologic and Water Quality Findings
The 2017 Water Year was a very wet year for Cache Creek, the Sacramento River Valley, and the state of California. The Sacramento River Index classified 2017 as a “wet” year for the Sacramento River, which produced more than double the total runoff in 2017 as in 2016. The 2017 water year was wetter than has been observed for several years. Flows at Yolo exceeded 2,000 cubic feet per second (cfs) continuously between early January and mid-March 2017. During this period, there were multiple large runoff events, including nine above 10,000 cfs, four above 15,000 cfs, and two above 20,000 cfs. This hydrology in 2017 produced some dramatic changes in Cache Creek including significant sediment transport and channel change. Water quality sampling data remained within or below the ranges measured in previous years and did not exceed any recommended contaminant limits. Some contaminants continued to be not detected in water year 2017 as in the last several years.
Geomorphology Findings
As mentioned in Section 1.3.1 of the report, Water Year 2017 was extremely wet, which led to significant activity with respect to geomorphology. Flows exceeded 20,000 cfs (approximately a 5-year event) twice, and were above 10,000 cfs for extended periods of time. More sediment was transported in Water Year 2017 than in the entire period between 2007 and 2016. Water Year 2006 was the last year with a similar level of geomorphic activity as Water Year 2017. While the peak flow in Water Year 2006 exceeded the peak flow in Water Year 2017 (29,900 cfs in 2006 vs. 21,200 cfs in 2017), Cache Creek experienced more peak flow events and significantly longer periods of elevated flows in 2017 than in 2006. Widespread channel change including bank erosion, bed scour, and bed deposition occurred in 2017 and may have been even more extensive than in 2006 due to the multiple periods of increasing and decreasing flows and the extended periods of elevated flows.
All locations with previously documented channel change experienced change in Water Year 2017, and some new locations changed significantly and have been added to the list of sites monitored by the Cache Creek TAC. In addition, Cache Creek appears to have shifted from a net-depositional condition between 1997 and 2011 to a net-erosional condition between 2011 and 2017. The net loss of sediment from the CCRMP area during this period was largely driven by the extensive bank erosion and lateral channel migration that occurred in Water Year 2017. Therefore, there were still large areas (primarily mid-channel bars) that were net-depositional during this most recent period where bar skimming and other in-channel maintenance actions could improve stability in Cache Creek.
Biological Resources Findings
The condition of biological resources in 2017 was markedly different than conditions observed in 2016, primarily due to the significant loss of vegetation caused by high flows (see Chapter 5 of the Annual Report). Herbaceous vegetation that had been observed increasing in the main channel in recent years was scoured away in many locations. Large patches of woody vegetation, including both willow scrub and riparian forest, were also removed along banks in several reaches due to channel meander and subsequent erosion. In addition, at least one past revegetation project was almost completely washed away. Native vegetation was again observed to be creating potentially adverse conditions in some locations; however, no actions are yet required other than continued annual monitoring.
Invasive species are still widespread in many locations along lower Cache Creek, although the intensive treatment of arundo, ravennagrass, and tamarisk that has occurred since 2006 with funding from the Wildlife Conservation Board has greatly reduced the extent of these three species. However, many additional invasive species (e.g., Himalayan blackberry, perennial pepperweed, and tree tobacco) are now common along lower Cache Creek, and should be prioritized for treatment and monitoring. After treatment, native species should be planted to enhance habitat and reduce the potential for reinvasion.
Many common and special-status species of wildlife, invertebrates, and fish were again observed by the TAC and others during the annual Creek Walk. Special-status species observed included Swainson’s hawk (State threatened), and Western pond turtle (State species of special concern). Additional species of note included mink, Mexican free-tailed bat, blue grosbeak, least sandpiper, lesser nighthawk, and red-shouldered hawk.
Significant opportunities for habitat enhancement and restoration were again noted in 2017, including the PG&E “Palisades” (River Mile [RM] 26.8), the Hayes “Bow-Tie” property (RM 20), the Millsap property (RM 18.5), the Wild Wings property (RM 17), and the Correll-Rodgers properties. Based on 2017 Creek Walk observations, the long-term resilience of revegetation and restoration projects within or adjacent to the active channel should be carefully considered prior to implementation, since such projects can be negatively impacted or completely removed by high flows. |