STREAM INVENTORY REPORT
Hatch Gulch is a tributary to the Big River (Figure 1). Elevations range from 100 feet at the mouth of the creek to 600 feet in the headwater areas. Hatch Gulch’s legal description at the confluence with the Big River is T17N R16W Sec25. Its location is 39°18'13"N. latitude and 123°35'59"W. longitude according to the USGS Comptche 7.5 minute quadrangle.
HABITAT INVENTORY RESULTS
The habitat inventory of July 9, 1996 through was conducted by Diana Hines and Dave Wright. The total length of surveyed stream in Hatch Gulch was 2,880 feet (.55 miles, .87 KM) (Table 1). There were no side channels in this creek. Flow measured at the mouth of Hatch Gulch on 07/09/96 was .07 cubic feet per second (cfs).
Hatch Gulch consists of one reach: A G4 for the entire 2,880 feet of creek.
Table 1 summarizes the Level II Riffle, Flatwater and Pool Habitat Types. By percent occurrence Riffles comprised 18%, Flatwater 32% and Pools 44% of the habitat types (Graph 1). By percent total length, Riffles comprised 10%, Flatwater 53% and Pools 44% (Graph 2).
Twelve Level IV Habitat Types were identified and are summarized in Table 2. The most frequently occurring habitat types were Mid Channel Pools 27%, Step Runs 24% and Low Gradient Riffles 12% (Graph 3). The most prevalent habitat types by percent total length were Step Runs at 45%, Mid Channel Pools 14% and Dry Units 14% (Table 2).
Table 3 summarizes Main, Scour and Backwater pools which are Level III Pool Habitat Types. Main Channel Pools were most often encountered at 60% occurrence and comprised 58% of the total length of pools.
Table 4 is a summary of maximum pool depths by Level IV Pool Habitat Types. Pools with depths of two feet (.61 m) or greater are considered optimal for fish habitat. In Hatch Gulch, 6 of the 40 pools (15%) had a depth of two feet or greater (Graph 4).
The depth of cobble embeddedness was estimated at pool tail-outs. Of the pool tail-outs measured, 0% had a value of 1, 3% had a value of 2, 22% had a value of 3 and 76% had a value of 4 (Graph 5).
Of the Level II Habitat Types, Riffles had the highest mean shelter rating at 61 (Table 1). Of the Level III Pool Habitat Types, Backwater Pools had the highest mean shelter rating at 120 (Table 3).
Of the 40 pools, 10% were formed by Large Woody Debris: 10% by logs and 0% by root wads (calculated from Table 4).
Table 6 summarizes dominant substrate by Level IV Habitat Types. Of the Low Gradient Riffles fully measured, none had gravel or small cobble as the dominant substrate (Graph 6).
Mean percent closed canopy was 86%: 50% coniferous trees and 36% deciduous trees. Mean percent open canopy was 14% (Graph 7, calculated from Table 7).
Table 7 summarizes the mean percent substrate/vegetation types found along the banks of the stream. Mean percent right bank vegetated was 80% while mean percent left bank vegetated was 78%. Coniferous trees were the dominant bank vegetation type in 58% of the units fully measured. The dominant substrate composing the structure of the stream banks was cobble/gravel found in 53% of the units fully measured.
The information gathered in the process of habitat typing will provide Georgia-Pacific with baseline data on the current condition of this creek and the available habitat for salmonids. These data can be used to identify components of the habitat which are in need of enhancement so appropriate conditions for Hatch Gulch can be obtained over time.
Level II habitat types by percent occurrence and length
Flatwater habitat types comprised a moderate percentage of the units by percent occurrence at 32% and a high percentage of the units by length at 53% (Table 1 and Graph 1). These unit types usually do not provide optimal spawning or rearing habitat for salmonids. Riffle habitat units comprised a low percentage of the stream by both percent occurrence and length at 18% and 10% respectively. Pools comprised a high percentage by percent occurrence and a moderate percent by length at 44% and 24% respectively. Riffles usually provide good spawning habitat while pools provide important rearing habitat. In addition, Mundie (1969) reported that invertebrate food production is maximized in riffles while pools provide an optimum feeding environment for coho. In fact, the most productive streams are those consisting of a pool to riffle ratio of approximately one to one (Ruggles 1966).
According to Flosi and Reynolds (1994), a stream with 50% of its total habitat comprised of primary pools is generally desirable. Primary pools are at least two feet deep in first and second order streams and at least three feet deep in third order streams. The information from Graph 4 on maximum depth in pools was used to determine percent of primary pools. Hatch Gulch, a third order stream, is comprised entirely of shallow pools with none of the pools having a maximum depth of three feet or greater.
Instream shelter ratings are derived from two measurements: instream shelter complexity and instream shelter percent cover. The first is a value rating which provides a relative measure of the quality and composition of the shelter, and the second is a measure of the area of a habitat unit covered by shelter. The various types of instream shelter include LWD, SWD, boulders, root wads, terrestrial vegetation, aquatic vegetation, bedrock ledges and undercut banks. Of the Level II habitat types Riffles had the highest shelter rating at 61. Of the Level III habitat types Backwater Pools had the highest shelter rating at 120. The first value is low while the second is high as shelter values of 80 or higher are considered optimal for good rearing habitat (Flosi and Reynolds 1994).
Large Woody Debris
The presence of Large Woody Debris (LWD) in streams is a significant component of fish habitat. Woody debris creates areas of low flow, providing a refuge for fish during periods of high flow (Robison and Beschta, 1990). Woody debris also provides cover for fish, lowering the risk of predation. The percent of pools formed by LWD in Hatch Gulch was 10%. Whether these numbers are high or low, relative to the needs of salmonids is difficult to ascertain since the optimum amount of woody debris in streams has not been specified (Robison and Beschta 1990). However, based on data from Georgia-Pacific’s 1995 Aquatic Vertebrate Study, the only coho found in the Ten Mile River Basin were in stream reaches where approximately 50% of pools were formed by large woody debris. Those reaches that did not support coho had a significantly lower percentage of pools formed by large woody debris (Ambrose et al, 1996). This suggests that a low percentage of LWD formed pools could adversely affect juvenile Coho Populations (C.S. Shirvel 1990).
The above LWD analysis pertains only to pools formed by logs or root wads as described in Flosi and Reynolds (1994): Lateral Scour Pool Log Enhanced, Lateral Scour Pool Root Wad Enhanced, Backwater Pool Log Formed and Backwater Pool Root Wad Formed. Other pools containing LWD as a component were not included in the calculation. For example, plunge pools may be formed by boulders, bedrock or LWD but are not described as such by habitat unit types. Therefore, the LWD formed pool calculation is limited to four pool types and does not quantify the total amount of LWD in Hatch Gulch.
There are two important benefits of canopy cover in coastal streams. Canopy keeps stream temperatures cool as well as providing nutrients in the form of leaf litter and organic material (Bilby 1988). This leaf litter, organic material, and their associated nutrients are utilized as a food source by benthic macroinvertebrates (aquatic insects). The macroinvertebrates, in turn, are major food sources for most fish species in forested areas (Gregory et al., 1987). Mean percent canopy cover for the Hatch Gulch was 86%. This is relatively high since a canopy cover of 80% or higher is considered optimum, Flosi and Reynolds (1994).
Coniferous trees occupied a larger portion of the canopy than did deciduous trees. Coniferous trees comprised 50% and deciduous trees 36% of the canopy. Wood from coniferous trees does not deteriorate as rapidly as wood from alder and most other deciduous species (Sedell, et al. 1988). Therefore, more LWD would be available in the future for fish cover and LWD formed pools in this creek and others dominated by coniferous species.
High embeddedness values (silt levels), such as those found in Hatch Gulch, have been associated with many negative impacts to salmonids. These negative impacts can be observed in important environmental components of salmonid habitat, such as Pool habitats, dissolved oxygen levels and water temperatures.
The impact high silt levels have on pool habitat is that they fill in and eventually eliminate pools. As already mentioned, pools provide important habitat for rearing salmonids.
High silt levels also impact oxygen levels in the water. They do so by reducing water circulation within the substrate, thus lowering the oxygen levels needed by salmonid eggs (Sandercock, 1991). This can hinder the survival of the eggs deposited in the redds, as well as the survival of juvenile salmonids.
Water temperature is impacted by high silt levels in several ways. Hagans et al (1986) reported the following impacts to water temperatures: 1) the loss of a reflective bottom; 2) darker sediment (as opposed to clean gravels) storing heat from direct solar radiation which is then transferred to the water column; and 3) a reduction in the flow of water through the substrate interstitial spaces thereby exposing more of the water column to direct solar radiation.
Another means by which water temperatures are increased is through the widening of stream channels: over time, high silt levels increase the substrate surface level of the creek, resulting in a wider, shallower stream channel (Flosi and Reynolds, 1994). In shallow streams more surface area is exposed to the sun relative to the volume of water, leading to an increase in solar heating which in turn leads to higher water temperatures.
Substrate embedded with silt in varying degrees were given corresponding values as follows: 0-25%= value 1, 26 - 50% = value 2, 51 - 75% = value 3 and 76 - 100% = value 4. According to Flosi and Reynolds (1994), creeks with embeddedness values of two or higher are considered to have poor quality fish habitat. In the Hatch Gulch, 100% of the pool tail-outs measured had embeddedness values of two or more.
It is important to consider, however, that the above embeddedness values were obtained in the summer during low flow conditions. In winter and spring, flows are usually higher due to the rainy season and the lowered evapotranspiration of the trees. This higher flow can carry away some of the previously deposited silt to sites further downstream. Therefore, embeddedness values may fluctuate throughout the year along different sections of the stream.
In Hatch Gulch, 100% of the Low Gradient Riffles had large cobble as the dominant substrate. The absence of gravel or small cobble in riffles indicates that there is an insufficient amount of substrate available as potential spawning habitat in this creek. In addition to having insufficient substrate for spawning in the riffles surveyed, the overall percentage of riffles in the surveyed portions of the creek was low at only 18% (Table 1). Subsequently, there may be a lack of sufficient spawning habitat in this creek as well. Another point to consider is that regardless of the amount of substrate or spawning habitat available, this habitat may not be suitable for salmonids if it is highly embedded.
Overall, Hatch Gulch appears to have insufficient substrate for spawning as well as insufficient spawning habitat, high embeddedness values and a relatively low percentage of primary and LWD formed pools. This creek does appear to have sufficient canopy.
Georgia-Pacific recognizes that there are areas of Hatch Gulch in need of enhancement, and where feasible will attempt to restore those areas over time as part of its long term management plan. The company will also attempt to facilitate a healthy environment for salmonids in this creek through sound management practices.
Hatch Gulch should be managed as an anadromous, natural production watershed.
Where feasible, design and engineer pool enhancement structures to increase the depth of pools. This must be done where the banks are stable or in conjunction with stream bank armor to prevent erosion.
Log debris accumulations retaining large quantities of fine sediment should be modified if necessary, over time, to avoid excessive sediment loading in downstream reaches.
Sources of stream bank erosion should be mapped and prioritized according to present and potential sediment yield. Identified sites should then be treated to reduce the amount of fine sediment entering the stream. In addition, sediment sources related to road systems need to be identified, mapped and treated according to their potential for sediment yield to the watershed.
Spawning gravel in this creek was limited. Projects should be designed at suitable sites to trap spawning gravel in order to increase spawning habitat throughout the stream.
The following memos were taken in the field at the time of survey. All distances are approximate and measured in feet from the confluence.
379 One young of year (yoy) observed
558 Yoy observed
609 Possible hobo temp pool
878 Pileated woodpecker heard
1029 Log jam over pool 3'h x 8'w x 2'l
1142 No fish observed
2025 Tributary entering left bank at end of unit
2880 End of survey, End of Anadromy. creek is barely flowing above dry unit. no suitable spawning habitat observed for last 1000' approximately. no fish observed almost entire survey (since unit #16). creek is highly embedded and highly entrenched in most units.