Laserfiche WebLink
Level loop Vertical elevations were established throughout each habitat type by surveying a <br />level loop in the transect headpins using differential leveling (Trihey and Wegner 1981). In <br />addition to the transect headpins, a benchmark was established and assigned the arbitrary <br />elevation of 100.00 feet. All differential leveling was in reference to this benchmark. Level <br />loops were closed to the specifications listed in Trihey and Wegner (1981). <br />Transect specific measurements At each transect, the model requires the following data: stream <br />bed profile, total depth at each wet vertical, mean column or nose velocity at each vertical, water <br />surface elevation, linear distance between transect headpins, substrate composition, and cover <br />type. The following procedures were used to obtain the necessary data. <br />Streambed profile A tape was attached to the working pins to delimit the transect <br />endpoints and to establish stationing for the verticals. A 30 power Topcon Auto level <br />was used for surveying all bed profiles. The level was set in line with the transect and the <br />headpin used to establish relative elevations. Starting at the "zero" station on the tape and <br />progressing to the opposite bank working pin for all above water locations, the stream <br />bed elevations were surveyed to the nearest 0.1 foot. At the water's edge on both banks, <br />the station was noted and water surface elevation surveyed to the nearest 0.01 foot. This <br />elevation was used as a reference for all wet verticals. Bed elevations for all in -water <br />verticals were calculated by subtracting the water depth from the water surface elevation. <br />Water depth Starting at the water's edge and progressing across the stream at one foot <br />intervals, water depths were measured to the nearest 0.1 foot using a top- setting wading <br />rod. Total water column depth was measured at each vertical. <br />Water velocity At each vertical where depth was measured, mean column water velocity <br />was measured using a Swoffer Model 2100 current meter. The habitat suitability criteria <br />use mean column velocity in the suitability calculations. Mean column velocity was <br />measured at 0.6 times the total depth from the water surface. Velocities were recorded to <br />the nearest 0.01 foot per second. <br />Substrate composition Substrate composition was visually estimated at all verticals both <br />wet and dry. Substrate was categorized by percentage of dominant and subdominant size <br />class. The following categories were used to describe the substrate at each vertical: <br />Aquatic vegetation <br />Silt <br />Sand <br />Small gravel (0.25 - 1.0 inch diameter) <br />Large Gravel ( >1.0 - 3.0 inch diameter) <br />Cobble ( >3.0 - 10.0 inch diameter) <br />Boulder ( >10.0 inch diameter) <br />Bedrock <br />Minimum Flow Study, South Fork of the South Platte River — Final Report Page 5 <br />February 19, 2001 <br />