		\| Background \| Hypotheses \| Bibliography \| Maps \| Home

Riparian Information in KRIS Gualala

KRIS Web Background Pages: Riparian Areas

The KRIS Gualala project contains several useful indicators of riparian condition. The KRIS database has canopy cover information from habitat typing surveys and the KRIS Gualala Map project provides forest stand data from the U.S. Forest Service Pacific Southwest Region Remote Sensing Lab. The vegetation coverage can be filtered to show only a buffer of 90 meters (297 feet) immediately adjacent to both sides of the stream (1:24000 USGS DRG). Summary data from this coverage is also displayed as charts in the KRIS database. The 90 meter area was chosen to represent a zone of influence that contributes large wood and helps control microclimate over the stream. Keithley (1999) pointed out that conifers larger than 24 inches in diameter were needed to provide large wood supply to maintain aquatic habitat diversity. Change scene detection between 1994 and 1998 using Landsat imagery can show where timber harvests have fallen with the 90 meter buffer in that period (see background page Tree Size and Vegetation Types). The U.S. Geologic Survey (USGS) digital orthophotos, which are compressed for use in the KRIS Gualala Map project, also provide a reconnaissance tool for assessing riparian health.

The KRIS Gualala database contains canopy cover information from habitat typing surveys provided by the California Department of Fish and Game (CA RA, In Review) and the Sotoyome Resource Conservation District. This information can be used to gauge stream health (see Habitat Typing background page). Canopy is measured with a densiometer. One problem with canopy information is that is does not indicate riparian over-story conditions, which effect microclimate and large wood recruitment potential (see Riparian Function and Protection Background page and Hypothesis #5).

	The upper North Fork Gualala watershed (Billings Creek Calwater) may have naturally high components of small diameter trees and non-forest due to bedrock geology as shown by the USFS vegetation map at left. However, the young age of the riparian forest in the western North Fork basin is largely a result of timber harvest. Natural open canopy conditions in the upper basin leave the stream open to warming but small diameter trees in the western basin also promote warming and indicate a lack of potential large wood for recruitment into the stream for salmonid habitat.
	The riparian zone of the Robinson Creek Calwater in the North Fork Gualala basin as of 1994 had more than half its riparian zone in very early seral stage conditions (<20 " diameter) with 25% of trees less than 12". This indicates recent timber harvest in this zone and that there is a shortage of large trees next to the stream to supply large wood. This Calwater includes much of the lower mainstem North Fork as well as Robinson, McGann and Dry creeks.
	Vegetation and timber types of the riparian zone of the Billings Creek Calwater are displayed at left and shows high components of Non-Forest (17%) and Saplings. This is largely natural because it has large areas of grassland and oak woodlands as a result of underlying Central Belt Franciscan terrain.

	This image shows the Stewart Creek Calwater with a 90 meter buffer riparian zone and 1994 and 1998 change scene detection. Red (>70%) and orange (40-70%) indicate that there has been substantial timber removal within the 90-meter buffer area on both the mainstem North Fork and its tributaries, particularly Hayfield Creek (at upper right) and Lost Creek. The latter is a tributary of Dry Creek that was grouped with the Stewart Creek Calwater (at left). Also of concern are the steep inner gorge areas and headwaters harvested. The latter are Class III streams and have less protection under California Forest Practice Rules.

thp_clearcut_sanandreas.jpg (87274 bytes)

Clear cuts show in the photo at left of the North Fork Gualala River looking south along the San Andreas Fault. The clear cuts abut the 100-foot watercourse and lake protection zone (WLPZ). Because the USFS 90 meter riparian buffer has a one hectare resolution, tree size classes would be averaged with edge of the clear cut. Although these riparian zones afford shade, they are not sufficient to minimize airflow over streams (see Temperature Background page), and thus to fully protect cool water temperature regimes. Since redwoods may exceed 200 feet in height, if left to grow, harvests in the 100 to 200 foot band also deprive the stream of large wood.

Rockpile Creek's 90 meter riparian buffer for the Middle Rockpile and Red Rock Calwater planning watersheds are displayed at left. Natural grasslands in eastern Rockpile Creek give rise to Non-Forest, Saplings and Small Trees. However, the predominance of trees less than 20" in the Red Rock and the western Middle Rockpile Calwaters are a result of very recent timber harvest. Site potential in Rockpile Creek for conifer growth is high and original riparian trees were over 17 feet in diameter. Changes in the landscape between 1994 and 1998 based on Landsat images, shows a similar pattern of riparian and inner gorge harvest, which depletes potential large wood supply (see Hypothesis #5).

The map of the South Fork Gualala 90-meter riparian zone at left shows the influence of the Ohlsen Ranch formation, which is associated with Non-Forest and Saplings vegetation signatures. Very Large or Large Trees remain in the Middle South Fork Calwater Planning Watershed because there has been less recent active timber harvest. Consequently, this reach is important for buffering naturally warm temperatures from upland areas and for future large wood recruitment.

Vegetation stand types for the riparian zone of all Wheatfield Fork Calwater Planning Watersheds based on a 1994 Landsat image are displayed at left. Much of the riparian zones in eastern Calwaters show as Non-Forest, Saplings and Small Trees as a result of natural grasslands in mélange terrain of the Central Belt Franciscan. Annapolis, Fuller Creek, western Tobacco Creek and western Haupt Creek all have high site potential forest soils and small diameter trees in the riparian zone of these latter areas are indicative of past and recent timber harvest.

References

California Resources Agency. In Review. Gualala River Watershed Synthesis. CA Dept. of Fish and Game, State Water Res. Control Bd., CA Dept. of Water Resources, CA Div. on Mines and Geology and CA Dept. of Forestry. Sacramento, CA. Draft released January 16, 2001.

Keithley, C. 1999. Evaluating Stream and Watershed Conditions in Northern California. Prepared for the California Department of Forestry, Fire and Resource Assessment Program. Sacramento, CA. 17 pp.