ABSTRACT. The Mission Creek watershed was analyzed using Geographical Information Systems (GIS)

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1 ABSTRACT The Mission Creek watershed was analyzed using Geographical Information Systems (GIS) as well as field observations. The objectives were to characterize the vital components of the Mission Creek channel and water, as well as the modes of network evolution. It contains six unique lithologic units that span an area of roughly km 2. The watershed that passes over these lithologic units has a total stream length of 49.5 km, an average channel slope of 0.30 and a drainage density of 3.15 km -1. Significant locations along the watershed are detailed to analyze the drainage density, topographic profiles and crosssections to provide a framework to regionalize watershed management and stream resource management. Analysis of drainage density leads to streamflow sensitivity, and watershed analysis can provide a framework to regionalize watershed management and stream resource management. INTRODUCTION Objectives The objectives of this study include characterizing vital components of the Mission Creek channel and watershed including the bed configuration, channel pattern, drainage network (composition and density) and modes of network evolution. The factors that control the drainage density are vital to the report. In order to accomplish the extensive processes that comprise the Mission Creek channel and watershed, strategically chosen locations in the watershed or at locations heavily influenced by the watershed will be analyzed. Study Area The Mission Creek watershed begins in the Santa Ynez Mountains in Rattlesnake Canyon, channeling through the city of Santa Barbara, CA, until it empties into the Santa Barbara harbor. (Figure 1)

2 Figure 1 The Mission Creek watershed is located on the southern side of the Santa Ynez Mountain Range, north of Santa Barbara, California. It resembles a triangular shape from north to south draining to a singular vertex (McCuen 1998). The watershed extends roughly 14.2 kilometers from the ocean to the ridge of the Santa Ynez Mountains with an elevation change of 1.1 kilometers (Clyde 1999). Rattlesnake Creek is the one main tributary and Mission Creek is the main channel of the watershed. The area that drains as a result of the Mission Creek watershed is approximately 15.7 km 2 (See Figure 4). Santa Barbara has a Mediterranean climate with high concentrations of riparian and chaparral vegetation. Alluvial channels have nonlinear and dynamic tendencies, exhibiting a wide variety of responses to perturbations of hydraulic discharge or sediment supply (Buffington and Montgomery 1999). The watershed runs through an assortment of residential, urban and natural environments, making it an integral part of the local hydrologic cycle (Clyde 1999). Lagoon DESCRIPTION OF DRAINAGE BASIN The mouth of the watershed is a blind estuary, which indicates that the system is open in the winter when rainfall and streamflow are high, yet closed at the mouth by sandbars during the summer months due to low input of flow. Various processes, both environmental and anthropogenic, affect the ocean to lagoon access point barrier including

3 storm flows, waves and human-induced actions. Species that inhabit the lagoon are predominantly steelhead and tidewater Gobi. Channelized Reach The height of the banks extends about five meters. It is built near the harbor to contain a flood with a trapezoidal shape of cement and concrete material. No boulders, rocks or vegetation are present inside the reach, making the region devoid of roughness elements. Oak Park A channel has been constructed for facilitating fish migration, while also inhibiting sediment deposition. The streambed varies between gravel, cobble and boulder-sized sediment. The channel consists of manmade step pools. Boulders have been arranged by humans, yet they were less in diameter than at Rocky Nook or Skofield parks. All the reconstruction was done with the goal of establishing a more natural order to the region. Bankfull indicators include sycamore tree roots. Concrete gabions make up portions of the bank in some stretches of the river for bank reinforcement preventing bank from migrating. Rocky Nook At Rocky Nook Park very large boulders are present from a debris flow. There were remnants of a paleochannel, as the local area ran along Mission Ridge Fault. Wind and water gaps, valleys and openings (respectively) where water once flowed through or carved but had dried up were present. Less fine gravel and boulders than those at Skofield Park comprise the streambed. They were indications of a river likely established when the slope was at a lower elevation before the debris flow. A botanical garden nearby is influenced landscape-wise from an alluvial fan formation of kya (E. Keller, personal interview, 2013).

Skofield Park At Skofield an alluvial fan is present, and the region is also the origin of the 125 kya debris flow that influenced all the topographically lower region (E.

4 Skofield Park At Skofield an alluvial fan is present, and the region is also the origin of the 125 kya debris flow that influenced all the topographically lower region (E.Keller, Personal Interview 2013). A scarp, evidence of a landslide, is present and can be linked to the origin of the debris flow. Boulders present have the largest diameters observed in the watershed. Boulders can be termed immobile sediment (Best and Keller 1985). The shape of the velocity profile is strongly influenced by the size of the roughness elements on the channel bed. A very high relief and large roughness elements are also relevant geological elements of the area. GEOLOGY The study area is within the Western Transverse ranges, a tectonically active, semiarid region characterized by a high rate of denudation. (Warrick and Mertes 2009) Heavy influence from geologic and climatic factors results in the distinct variations of relief and uplift. (Figure 2) Figure 2 Digital Elevation Model of Santa Ynez mountain range and Santa Barbara. Compression from the uplift and lithologic composition generated rapid uplift, producing abundant east-west thrust faults, folds and strike-slip faults. (Warrick and Mertes 2009) The formations that comprise the study area range from Quaternary to late Eocene. The six main geologic units, in order of youngest to oldest, that comprise the watershed are: Quaternary Alluvium (Qa), Sespe Formation (Tsp), Coldwater Sandstone

5 (Tcw), Cozy Dell Shale (Tcd), Matilija Sandstone (Tma) and the Juncal Formation (Tjsh). (Figure 3) The Qa is landslide debris of unconsolidated alluvium (floodplain deposits of silt, sand and gravel) deposited during the quaternary period of the last 2.5 mya. The Tsp is a maroon, red and green silty shale or claystone of interbedded red, tan and gray sandstone of nonmarine origin and predominantly Oligocene age (geologic epoch from MYA). Red arkosic sandstone and conglomerates at the base of the Tsp formation are interspersed.

6 The Tcw is a tan, hard, bedded arkosic sandstone with minor interbedding of greenish-gray siltstone and shale of late Eocene age (geologic epoch from MYA). Local oyster shell beds are common, which correlate with the Tcw s marine origin. The Cozy Dell Shale is a marine, late Eocene argilaceous to silty micaceous shale of dark gray color. The Tcd has various light gray to tan arkosic sandstone rocks of Narizian stage origin. The Matilija Sandstone is of marine origin and late Eocene age (lower Narizian and Upper Ulatisian stages) with hard, thick bedded, tan arkosic sandstone along with thin partings of gray micaceous shale. The Tjsh formation is dark, gray micaceous shale with minor thin interbedding of hard, gray-white to tan arkosic sandstone. The Tjsh is of early to middle Eocene age. METHODS Drainage Density To determine the drainage density and area, keyhole markup language (kmz) (zipped files for expressing geographic annotation and visualization) were obtained from the University of California, Santa Barbara (UCSB) for use in the geographical information system Google Earth. The drainage density was calculated using the equation: Drainage Density = Total Length of Streams and Rivers in a Drainage Basin Total Area of the Drainage Basin Eight files were obtained from the university. The files show the drainage density, geologic units, mission creek, mission creek watershed, rattlesnake creek, Santa Barbara geologic map and a topographical map of Santa Barbara. Microsoft Excel tabular data for the sum of channel lengths in each geologic unit was also provided by UCSB. Data from Excel and Google Earth were combined to determine the drainage density. Topographic Profiles To determine the topographic profiles (longitudinal and cross-valley), kmz data provided by UCSB was utilized again in the digital programs Google Earth, Excel and Paint.

7 An elevation profile was extracted from Google Earth from the longitudinal profile kmz file and imported to Microsoft Excel. In Excel charts the distance from the ocean and the elevation above mean level were plotted against each other and lines were constructed to display the geologic unit boundaries. Cross-Valley profiles were also constructed by using Google Earth tools and Excel graphs to display onto the application Paint. RESULTS Drainage Density and Area The total stream length of the drainage basin is about 49.5 km with a drainage area of approximately 15.7 km 2. (Fig. 4). Figure 4 Mission Creek Watershed, Mission Creek, Rattlesnake Creek, Skofield Park Reach, Santa Barbara Botanic Garden Reach, Rocky Nook Park reach, Oak Park Reach, Channelized Reach, Lagoon

8 The result for drainage density was 3.15 km -1. Drainage densities were also calculated for each geologic unit and can be seen in Figure 5. Geologic Unit Total Stream Length within Unit (km) Qa 5.8 Tsp 4.7 Tcw 15.1 Tcd 8.5 Tma 7.5 Tjsh 7.8 Watershed Average 49.5 Geologic Unit Area (km 2 ) Drainage Density (km -1 ) Qa Tsp Tcw Tcd Tma Tjsh Watershed Average Geologic Unit Vertical Relief (km) Qa 0.12 Tsp 0.15 Tcw 0.26 Tcd 0.23 Tma 0.23 Tjsh 0.80 Watershed Average 0.30 Geologic Unit Channel Slope within Unit Distance From Ocean Along Longitudinal Profile Qa kilometers Tsp Longitudinal Profile Does Not Cross Tcw kilometers Tcd kilometers Tma kilometers Tjsh 0.7 Longitudinal Profile Does Not Cross Watershed Average 0.303

9 Topographic Profiles The vertical relief calculates the difference between elevation of highest point in the area and lowest point in the area. The average vertical relief for the watershed is 0.30 km with the results for each geologic unit in Figure 5. The average vertical relief is the difference in elevation between the highest and lowest points in a given area. The channel slope, a measure of the water surface or stream bed slope change in elevation over a defined distance, of the watershed is 0.25 and the results of each geologic unit can be seen in Figure 5. The channel slope was measured along the longitudinal profile of Mission Creek (Figure 6). Longitudinal Profile of Mission Creek with Geologic Units Tma 1.2 Tcw 14.2, Qa Tcd , 0.84 Elevation above mean sea level (kilometers) , , , , , , , , , , , Distance from Ocean (kilometers) Figure 6 Longitudinal Profile of Mission Creek with Geologic Unit Boundaries

10 Cross-valley profiles constructed from Google Earth were created across Mission Creek for the Coldwater Sandstone and Cozy Dell Shale geologic units (Figure 7) Cross Section of Mission Creek in Tcw 0, , , , Elevation above mean sea level (meters) , , , , , Distance (meters)

11 Cross Section Profile of Mission Creek Tcd Unit , , , , Elevation above mean sea level (meters) , , , , , Distance (meters) Figure 7 Cross Valley Profiles of Mission Creek Coldwater Sandstone and Cozy Dell Shale Formations

12 Cross-section profile analysis shows the Coldwater unit as slightly more steep than the Cozy Dell unit. DISCUSSION The composite slope distribution (0.30) infers the region in the study can be classified as to Montgomery and Buffinton s definition of a cascade channel type. (Montgomery and Buffington 1997) The cascade channel types exhibits geomorphologic characteristics such as a boulder bed material; fluvial, hillslope and debris flow as the dominant sediment sources; a slope of 0.30; and grains and banks as the dominant roughness elements. It is this distinctive and orderly fluvial geomorphology, some manmade (Oak Park step-pools) and some natural (Skofield Park debris flow), that illustrates the complexity of Mission Creek. The cross sections analyzed in the report imply that the hillslopes upstream have fluctuated according to channel adjustment processes such as the debris flow. The wide variation in slope influences the entire region (Figure 5), from determining particle size to the Channelized Reach and the construction of floodprevention structures to accommodate. The Cross-Valley profiles of the Coldwater Sandstone and Cozy Dell Shale have variances that are clearly evident. Each have similar drainage densities and slopes, yet the channel bed width for the Tcd formation is approximately 55 meters wide, while the Tcw formation has approximately a channel bed width of 30 meters. These quantitative values listed above indicate that one formation has stronger lithologic properties. The Tcw has the narrower channel bed, leading the supposition that the unit is stronger than the Tcd formation. Drainage density indicates how dissected the landscape is by channels, thus it reflects both the tendency of the drainage basin to generate surface runoff and the erodibility of the surface materials. Regions with high drainage densities will have limited infiltration, promote considerable runoff, and have at least moderately erodible surface

13 materials. Drainage density variations are not as drastic as the slope dimensions (Figure 5), yet comprise just as significant of an impact on the fluvial geomorphology of the study area. The Tsp formation has the lowest drainage density (2.45 km -1 ), which is not a result of its lithologic strength, but of its slope, which is the second lowest among the geologic units (0.099). Of the geologic units with recorded drainage density, the highest was Qa with a drainage density of 3.79 km -1. The Qa geologic unit is not composed of hard lithologic material and is the geologic formation with the lowest strength. The Qa unit s highest drainage density among the geologic units is compounded by it containing the lowest slope (0.055). A high drainage density is a sign of a high amount of streams and tributaries, leading to a relatively rapid hydrologic response to rainfall events; while a low drainage density infers a poorly drained basin with a slow hydrologic response. CONCLUSION The watershed geomorphology is integral in stating the components that constitute the transfer function. (McCuen, 1998) The impact of the debris flow and westward movement of Mission Creek by the Mission Ridge fault have vital influences throughout the watershed, as evident by the paleochannels or change in boulder size, a strong indicator due to the significant diameter changes. Analysis of drainage density leads to streamflow sensitivity, and watershed analysis can provide a framework to regionalize watershed management and stream resource management. The drainage density of the geologic units varies considerably across the length of the watershed, from 2.45 km -1 to 3.79 km -1. The area of the geologic units varies from 1.53km 2 for the Qa to 4.49km 2 for the Tcw. The channel slope of the geologic units also varies considerably from for the Qa to 0.7 for the Tjsh. The broad range of the watershed characteristics demonstrates the vast influences that act upon the watershed. The paleohydrologic implications of the region must be considered when analyzing the watershed due to the variability from the head of the watershed to the mouth.

14 While cross-section, longitudinal profiles and drainage density calculations are vital elements to conceptualization of watershed management, more in-depth geological analysis of the units incorporating soil permeability, precipitation-soil response analysis, groundwater influence and strength of the rock. These factors are as key to watershed management and incorporation would likely lead to a more comprehensive understanding of the Mission Creek Watershed s distinctive characteristics. References Best, D. W., & Keller, E. A. (1985). Sediment storage and routing in a steep boulder-bed rock-controlled channel. Retrieved from Buffinton, J. M., & Montgomery, D. R. (1999). Effects of sediment supply on surface textures of gravel-bed rivers. Water Resources Research, 35(11), Retrieved from b_WRR.pdf Keller, E. (2013, April 6). Personal interview. McCuen, R. (1998). Hydrologic analysis and design. (2nd ed., p. 100). Upper Saddle River, NJ: Prentice-Hall, Inc. Santa ynez mountains and santa barbara. (2009). Retrieved from a2_persp.jpg URS Greiner Woodward-Clyde. (n.d.). South coast watershed characterization study: An assessment of water quality conditions in four south coast creeks. (1999). Retrieved from Quality Reports/scwc.final.pdf Viveen, W. W., Schoorl, J. M., Veldkamp, A. A., van Balen, R. T., Desprat, S. S., & Vidal-Romani, J. R. (2013). Reconstructing the interacting effects of base level, climate, and tectonic uplift in the lower Miño River terrace record: A gradient modelling evaluation.geomorphology, doi: /j.geomorph Warrick JA, Mertes LAK (2009). Sediment Yield from the tectonically active semiarid Western Transverse Ranges of California, Geol Soc Am Bull 121:

Flood Frequency and Hazard Analysis of Santa Barbara s Mission Creek

Flood Frequency and Hazard Analysis of Santa Barbara s Mission Creek Dylan Berry Andrew Donnelly Bruce Stevenson Dr. Professor Ed Keller ES 144: Rivers UC Santa Barbara Spring 2013 Abstract: The objective