1. Water Canyon Geomorphology on Santa Rosa Island,
Water Canyon Watershed Geomorphology on Santa Rosa Island,
Channel Islands National Park
Dylan Fadich
Environmental Science & Resource Management, California State University Channel Islands
Water Canyon Geomorphology on Santa Rosa Island,
Channel Islands National Park
Dylan Fadich¹ and Dr. Linda O’Hirok²
ESRM Program
Introduction
Fluvial geomorphology is the study of river and stream dynamics and their influences on forming the landscape. I characterized Water Canyon watershed on Santa Rosa Island, studying large scale geomorphological changes from upstream to downstream sections of the stream channel. My hypothesis is that there will be large scale geomorphological changes throughout the stream channel due to faulting and other environmental factors. By setting baseline data, future research can be used to assess and calculate stream channel change as well as erosion and deposition rates. Interpreting the historic landscape formation of the different watersheds is helpful for making management decisions and to understanding the overall watershed system processes of erosion and sediment deposition throughout the island.
Results
Average percent slope for entire watershed 3.31%, Upstream of fault 3.78%, Downstream of Fault 2.72%
Average Depth Survey Sites 2-5 (downstream fault) meters, Average depth sites 13,15,19,21 (Upstream of fault) 5.37 Meters
Given that stream channel slope is consistently gradual, variances in stream channel dimensions suggest that faulting has caused more bedrock exposure and an increase in consolidated sediment downstream of the fault which in turn has led to a much more stabilized stream channel. Upstream of the fault consists of unconsolidated sediment, higher meander frequency, and shallower channel depth suggesting that this portion of stream channel is more unstable and susceptible to change and erosion
Methods
There are 24 survey sites throughout Water Canyon watershed from the uppermost reaches to the lowermost outlet. Sites were chosen to capture a variety of stream channel dynamics. I used a Nikon 5.c Total Station to take cross-sections, recording the shape of the stream channel using the slope distance and change in elevation measurements. These cross sections allowed me to observe stream channel dynamics and make physical comparisons between upstream and downstream portions of the watershed. Using ArcMap and Lidar imagery of the island I was able to calculate the depth and percent slope of the stream channel.
Discussion/Conclusion
The data shows how faulting has played a role in stream channel formation. Future research will be beneficial because it can be referenced to my data to show stream channel morphology as well as sediment erosion and deposition rates throughout the stream channel. This is important because the loss of vegetation from ranching has caused exponential erosion rates upstream. This data can also be used to help determine if there needs to be active restoration in water Canyon.
Acknowledgements
Thanks to Dr. Linda O’Hirok, Dr. Cause Hanna, Dr. Sean Anderson, the CSUCI ESRM program, and all the volunteers who helped collect data.