Six geomorphic study reaches were established in 2002 along a forested mountain stream (gradients range from 0.02 to 0.05) on Cal Poly's Swanton Pacific Ranch in Santa Cruz County, California. These study reaches are a component of paired and nested watershed studies in the approximately 500 hectare Little Creek watershed. The overall goal of this study was to monitor water quality and channel conditions before, during, and after a selective harvest of redwood. A selective harvest occurred in the North Fork of Little Creek in Summer 2008. In August 2009, approximately 90% of the Little Creek Watershed was burned in the Lockheed Fire. Channel change was evaluated by measuring ground profiles using traditional survey methods. Cross section and longitudinal profiles are surveyed annually every summer in the six study reaches. Change is assessed through evaluation of cross sections and longitudinal profiles, analysis of bed elevation and cross-sectional area change data, and analysis of residual pool characteristics and longitudinal profile variability. Changes in the channel during this time have been relatively small and are typically associated with movement or introduction of coarse woody debris to the stream channel. However, during the study period no large stream flow events occurred (return interval at the closest USGS gauging station does not exceed 5 years). Historically, large debris flow events have occurred in this watershed, with well documented events in 1955 and 1998. The survey data is an important tool for understanding change detection in channel characteristics before and after harvesting, and following fire disturbance.

Detecting change in stream channel features over time is important in understanding channel morphology and the effects of both natural and anthropogenic influences. Channel features historically, and now currently, are being measured using a variety of ground survey techniques. These surveys require substantial time commitments and funding to complete. Light Detection and Ranging (LiDAR) is an airborne laser mapping technology that holds promise to provide an alternative to ground-based survey methods. For this study, ground surveys were used to verify the accuracy of data collected using airborne LiDAR. Fifty nine cross-sectional profiles were surveyed in the Little Creek watershed at Cal Poly’s Swanton Pacific Ranch and compared to LiDAR-generated profiles of the same location. LiDAR data were collected in two flights during April and May of 2002. The vertical accuracy of LiDAR elevations was determined to be 0.610 m RSME based on a point-to-point comparison of the elevation of ground survey points in each cross-sectional profile to the corresponding LiDAR elevation. The average ground spacing of the LiDAR survey within the study area was one point every 5.2 square meters. In comparison to ground surveys it was found that with this level of vertical precision and horizontal resolution it would be difficult to detect change in bankfull channel characteristics of a relatively small channel, such as Little Creek. These difficulties are largely attributed to poor point coverage in forested, steep, and mountainous terrain, along with technological limitations of LiDAR that have since improved.