Year 3 Monitoring Report for The

Year 3 Monitoring Report for the

San Luis Obispo Creek Dam Removal and Steelhead Passage Enhancement Project

November 2005

Prepared by:

City of San Luis ObispoNatural Resources Program990 Palm StreetSan Luis Obispo, CA, 93455(805)-781-7511

Introduction/Purpose

On January 17, 2003 the City of San Luis Obispo completed a project to facilitate steelhead trout (Oncorhynchus mykiss) passage over a disused diversion dam on San Luis Obispo creek.

The dam is located on San Luis Obispo Creek, south of the Cuesta grade at Stagecoach road, north of the City of San Luis Obispo (Figure 1). Over one mile of potential spawning habitat in the upper reaches of San Luis Obispo Creek was inaccessible to steelhead trout prior to the project. The project restored steelhead access to the upper reaches of the creek, created a stable channel bed, and improved stream habitat in the area.

This monitoring report has been prepared to satisfy the requirements of the National Marine Fisheries Service (NMFS) Biological Opinion for the project, dated August 15, 2002.

The objective of the project was to restore access for migrating fish to over one mile of potential spawning habitat located above the dam, which was acting as an impassable barrier to fish passage. This involved:

Partial removal of the dam.
Construction of 20 rock weirs to provide gradient control both in the main channel and a tributary.
Channel fill/excavation above and below the dam.
Removal of one bay tree.

Installation of planted coir fiber logs at bank slopes; and the installation of erosion control blankets and hydro-seeding on newly graded bank slopes (given the dense shade of the site, there was no requirement for tree plantings, other than for four small bay trees).
Hand working of rock weirs.

Following completion of the project a monitoring program was to be implemented for a five-year period. The objective of this monitoring are twofold, first to ensure that the structural integrity of the step pool structure is maintained over time; and secondly, to determine if steelhead trout are able to traverse the structure and access potential spawning habitat above the dam as per the original intent of the project.

Methods

A number of parameters were measured for each of the 17 step pools in the structure. Three of the weirs have come apart through winter 2004 storm action but after consulting with DaveHighland from CDFG in September 2005, no passage issues were brought up. If recommendations for reworking some of the weirs from CDFG are warranted, this would occur in the summer of 2006. These parameters were then used to assess the ease with which steelhead could pass through the structure. The following parameters were quantified as detailed by Gallagher (1999).

Vertical height of each barrier; (height from the water surface at the plunge pool to the water level above the structure).
Pool Area; (distance from fall to pool tail multiplied by pool width).
Depth of pool in front of the barrier
Velocity of water flow over the barrier; (measured at a point just before water begins to fall over the structure).
Velocity of the tail water; (measured where water begins to flow out of the plunge pool).

This information was then used to assess the ease with which a steelhead of 50 mm (2”), 150 mm (6”) and 300 mm (12”) would be able to negotiate each weir in the structure. The assessment was done by completing the following questionnaire (Gallagher 1999) to determine if a structure was a barrier to fish migration.

Is the maximum jumping height of the fish higher than the height of the structure?
Is the darting speed of the fish faster than the velocity of the water flow over the structure?
Is the darting speed of the fish faster than the velocity of the tail water?
Is the depth of the plunge pool either greater than 1.25 times the height of the barrier or more than 2.5 m deep?
Does the plunge pool water return from turbulent to laminar flow within one-third the height of the structure? (One-third the height of the structure is a rough estimate to determine if the water is calm enough to allow the fish to reach maximum jumping height).
For anadromous fish, is the barrier less than halfway along the travel distance of the fish between the mouth of the river and the spawning ground? (The closer a fish gets to its spawning ground, the lower its maximum jumping height is likely to be due to increased levels of fatigue).
Are other environmental factors that could affect fish jumping abilities, such as temperature, within the ideal range required by migrating fish?

A positive answer to all the above questions indicates that a structure is probably not a barrier to fish movement under the prevailing conditions. The more ’NO’ answers given the more likely that a structure is a barrier to migrating fish. The results of this analysis are shown in tables 1 and 2.

Results

Analysis of the data in tables 1 and 2 indicates that it represents a significant barrier to small steelhead (length <50 mm), a partial barrier to intermediately sized juveniles (length ~150 mm), and is probably not a significant barrier to migrating adult fish (length 300 mm+).

Large adult fish (length 300 mm +) trying to reach spawning habitat above the dam should be able to negotiate the structure. However, the jump height/pool depth ratios of weirs 7, 8, 9, 14, and 18 are outside the acceptable ratio of 1:1.25 and may potentially hinder migrating adults.

Water temperature in the vicinity of the structure is within the optimal range for trout during migratory periods (i.e. ~9°C, Behnke).

Table 1. Measurements of dimensions and velocities at each weir. Weir 1 represents the downstream limits of the structure.
Weir # / Velocity over barrier (m/s) / Velocity at Tail
(m/s) / Pool Area
(m²) / Vertical Height
(m) / Pool Depth
(m) / Jump Height/Pool Ratio
1 / 0.68 / 0.36 / 16.91 / 0.41 / 0.91 / 2.22
2 / 0.72 / 0.40 / 10.03 / 0.25 / 0.49 / 1.96
3 / 0.82 / 0.26 / 13.27 / 0.20 / 0.46 / 2.30
4 / 0.82 / 0.27 / 14.30 / 0.25 / 0.58 / 2.32
5 / riffle / riffle / riffle / riffle / riffle / N/A
6 / 0.84 / 0.39 / 10.03 / 0.15 / 0.27 / 1.80
7 / 0.83 / 0.35 / 11.16 / 0.30 / 0.24 / 0.80*
8 / 0.61 / 0.29 / 6.69 / 0.27 / 0.27 / 1.00*
9 / 0.68 / 0.41 / 14.49 / 0.34 / 0.37 / 1.09*
10 / 0.98 / 0.35 / 5.20 / 0.15 / 0.21 / 1.40
11 / 0.76 / 0.42 / 2.78 / 0.15 / 0.21 / 1.40
12 / 0.60 / 0.45 / 1.85 / 0.24 / 0.37 / 1.54
13 / open / open / open / open / open / N/A
14 / 1.02 / 0.31 / 5.84 / 0.46 / 0.30 / 0.65*
15 / cascade / cascade / cascade / cascade / cascade / N/A
16 / 0.78 / 0.39 / 3.90 / 0.15 / 0.27 / 1.80
17 / 0.81 / 0.31 / 3.35 / 0.27 / 0.40 / 1.48
18 / 0.76 / 0.41 / 4.54 / 0.49 / 0.37 / 0.76*
19 / 0.83 / 0.28 / 9.18 / 0.18 / 0.34 / 1.89
20 / 0.82 / 0.27 / 8.93 / 0.25 / 0.37 / 1.48
* Deviation from recommended ratio (1:1.25)
** Marginal deviation from recommended ratio
Table 2. Matrix of answers to questions a-g for each weir in the structure.
0.05 m (2”) steelhead
v = (9l) = (9*0.05)= 0.45 m/s
h = v2/2g = .452/19.6 = 0.01m / 0.15 m (6”) steelhead
v = (9l) = (9*0.15)= 1.35 m/s
h = v2/2g = 1.82/19.6 = 0.093m / 0.30 m (12”) steelhead
v = (9l) = (9*0.15)= 2.70 m/s
h = v2/2g = 1.82/19.6 = 0.37m

Weir

/ a / b / c / d / e / f / g / a / b / c / d / e / f / g / a / b / c / d / e / f / g
1 /

N

/ N / Y / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y
2 / N / N / Y / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / Y / Y / Y / Y / Y / N / Y
3 / N / N / Y / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / Y / Y / Y / Y / Y / N / Y
4 / N / N / Y / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / Y / Y / Y / Y / Y / N / Y
5 / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / *
6 / N / N / Y / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / Y / Y / Y / Y / Y / N / Y
7 / N / N / Y / N / Y / N / Y / N / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / N / Y
8 / N / N / Y / N / Y / N / Y / N / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / N / Y
9 / N / N / Y / N / Y / N / Y / N / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / N / Y
10 / N / N / Y / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / Y / Y / Y / Y / Y / N / Y
11 / N / N / Y / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / Y / Y / Y / Y / Y / N / Y
12 / N / N / N / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / Y / Y / Y / Y / Y / N / Y
13 / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / *
14 / N / N / Y / N / Y / N / Y / N / Y / Y / N / Y / N / Y / N / Y / Y / N / Y / N / Y
15 / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / * / *
16 / N / N / Y / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / Y / Y / Y / Y / Y / N / Y
17 / N / N / Y / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / Y / Y / Y / Y / Y / N / Y
18 / N / N / Y / N / Y / N / Y / N / Y / Y / N / Y / N / Y / N / Y / Y / N / Y / N / Y
19 / N / N / Y / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / Y / Y / Y / Y / Y / N / Y
20 / N / N / Y / Y / Y / N / Y / N / Y / Y / Y / Y / N / Y / Y / Y / Y / Y / Y / N / Y

Visual Observations

No instream steelhead trout surveys were completed in 2005 but visual inspections through snorkel surveys will be initiated in 2006. Upon bank observation in July 2005, several fry were observed by the City biologist, Freddy Otte throughout the project area. The presence of fry above the notch in the dam shows a good likelihood of adult spawning above or within the project area.

Adult surveys will be conducted beginning in late January 2006. The presence of adult fish or redds will be noted based on bank observation.

Walking the site evaluating the weirs, numerous volunteer oak trees have been seen growing along the project site. The coir logs are still intact and collecting sediment from higher flows to aid in the natural revegetation of the project site.

Conclusions

The primary objective of the structure was to provide migrating adult steelhead access to potential spawning grounds above the dam structure. The presence of fry sized trout throughout the project area suggests that adult steelhead have been able to access the reach of creek above the dam. It is possible that the high jump height/pool depth ratios fish experienced at weirs 7, 8, 9, 14, and 18 could prevent steelhead from traversing the entire structure but the pool measurements were taken in September and under migration flows, passage should not be an issue. However, without further monitoring this cannot be proven at this time. As mentioned in the “Year 1” monitoring report, a potential barrier downstream of the dam has not been corrected but the City along with Caltrans will be addressing it in the near future.

The City will pursue Adaptive Watershed Management funds from the CDFG per the recommendation of DaveHighland to turn the metal notch at the dam structure around 180º so the plunge will be directly over the pool itself. The way it sits now, there is an added breadth of 5-inches due to the angle-iron weir being situated the way it is. See enlarged photo on page 9.

Although the project was completed in January 2003, one monitoring report has been submitted, this report is technically for the third year of performance for the structures but the second report to be submitted. The City is committed to following the progression of this project for several more years.

Redd surveys above the structure shall continue as the presence of redds will provide positive proof that adult steelhead are successfully negotiating the structure.

References

Behnke, R. J. 1992. Native trout of western North America. American Fisheries Society Monograph 6.

Gallagher S. A. 1999. Barriers. Pages 135- 148 in M. B. Bain and N. J. Stephenson, editors. Aquatic habitat assessment: common methods. American Fisheries Society, Bethesda, Maryland.

Appendix 1

Photodocumentation

San Luis Obispo Creek Dam Removal Monitoring Project –November 2005