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Hydrologic/Geologic Processes


Big Chico Creek originates from a series of springs, at an elevation of about 5,400 feet, northeast of the City of Chico on the southwest flanks of Colby Mountain. The watershed also encompasses three smaller drainages to the north: Sycamore, Mud, and Rock Creeks. Closest to Big Chico Creek is Sycamore Creek, which originates at around 1,600 feet and is a tributary to Mud Creek. Mud and Rock Creeks, further north, originate between 3,600-3,800 feet. Mud Creek drains off Cohasset Ridge to the south, flowing 26 miles to its confluence with Big Chico Creek. Rock Creek drains the north side of Cohasset Ridge and flows 28.5 miles before it joins Mud Creek. Big Chico Creek flows a distance of 45 miles from its origin, crossing portions of Butte and Tehama counties, to its confluence with the Sacramento River, at an elevation of 120 feet, west of the City of Chico.


The watershed is located in an Interior Mediterranean Climate that is defined by its moist, cool winters and hot, dry summers (Critchfield, 1974). The average yearly precipitation varies from 70-80 inches at Colby Mountain to about 20 inches at the Sacramento River (see Precipitation Map). Most of the precipitation falls as rain between the months of November to May, although during some of the colder winter storms a large amount of snow may fall above 3,000 feet. These events can bring snow to the headwaters of Mud and Rock Creeks as well. The snow pack adds to the regular base flow until it completely melts, usually by late spring. Snowpack can vary greatly, depending on how long and intense each winter is. Year to year climatic fluctuations can dramatically affect the flows in Big Chico Creek and its tributaries. Drought cycles and wet cycles have lasting effects and change the flow characteristics in the watershed and alter other interrelated natural processes. The temperatures for the area can drop well below freezing (<32°F) in the upper watershed during the winter and commonly rise above 100°F during July and August in the valley and foothill sections of the watershed.


The Big Chico Creek watershed is located in a region that includes the interface between the Sierra Nevada Range to the south, and the remnant volcanic flows of the Cascade Range to the north. Big Chico Creek originates in volcanic rocks, referred to as the Tuscan Formation. The Tuscan Formation, about 4 million years old, is the dominant geologic formation in the watershed as it is the most recent layer of material deposited on the landscape. The upper portions of the watershed are covered by the Tuscan, which as a relatively softer rock, allows the creek to disperse its energy more laterally than vertically, resulting in a flatter creek bottom. About one mile downstream of the confluence with Web Hollow, Big Chico Creek has eroded through enough of the Tuscan to expose a small stretch of “Sierran” rock (see Geology map). These rocks are also referred to as “Metavolcanic”, which means they originally came from volcanic processes but over time have been metamorphosed (changed) by heat and/or pressure. The Metavolcanic rocks are most likely old sea floors - ocean sediments, and associated materials - 225 to 500 million years old, that formed out in the Pacific Ocean. Over time there were many episodes of small land masses being pushed up against the edge of the continent, each time adding to the coastal terrain. These rocks are much harder than the Tuscan, restricting the creek and forcing it to disperse its energy by down cutting into the creek bed. The creek becomes more constricted in this area and the gradient (slope) of the creek increases. This approximately 4-mile stretch of metavolcanics is buried under the next geologic formation, the Chico Formation near Higgins Hole. The metavolcanics are the oldest rocks exposed in the watershed.

The Chico Formation is the second oldest geologic formation in the watershed, which is first exposed between Higgins Hole and where Ponderosa Way crosses Big Chico Creek (see Geology map). It is made up of sedimentary rocks composed of sands, silts, pebbles, and cobbles that made up the ancient shorelines when the Pacific Ocean reached into the Sacramento Valley. The Chico Formation is much softer rock than the metavolcanics and once again allows the creek to flatten out, dissipating its energy laterally. This results in a gentler gradient for this stretch of the creek. The Chico Formation is about 75 million years old and numerous marine fossils can be found within the sandstone.

Continuing downstream, the next oldest geologic formation, the Lovejoy Basalt, estimated at 20 million years, appears in the creek bed, upstream of the end of Upper Bidwell Park. The Lovejoy actually first appears as a layer between the Tuscan and the Chico, higher up on the canyon walls near Forest Ranch, where there is a

small “volcanic neck” that is most likely the source of the Lovejoy in Big Chico Creek canyon. From this point, down to where the Lovejoy layer is exposed in the creek, is mapped on the geology map as the Chico Formation. It is difficult to see the Chico Formation on the side slopes of the canyon due to large amounts of Lovejoy colluvium covering the area. The Lovejoy up in the cliffs is very fractured and breaks apart easily. Over time, pieces of the basalt, ranging from small cobbles to large boulders, have fallen off the cliff faces and covered large sections of the much gentler slopes of the Chico Formation below. Once the basalt is exposed along the creek, it once again restricts the stream, due to its hardness, and the gradient of the creek increases, forming Iron Canyon. Iron Canyon is the stretch of the creek from Brown’s Hole to Bear Hole in Upper Bidwell Park, with large piles of black basalt boulders in the creek.

The gradient of the creek is also likely affected by a series of northwest trending faults that cross the area. These faults are part of the Chico Monocline, which stretches along the foothills from Red Bluff to Chico.

In the northern part of the Monocline, closer to the City of Red Bluff, the faults are in much closer proximity to each other, causing a much steeper entrance to the valley. This pattern can be seen in Deer and Mill Creeks. Deer and Mill Creeks alluvial fans are much smaller because the flows, especially the geomorphically significant flows, are constricted in the valley reach by the Red Bluff Formation; a very resistant formation made up of cemented cobbles and gravels. This phenomenon occurs due to the high gradient of the creeks as they enter the valley, which causes most of the waters erosional force to be dispersed down vertically and less laterally. Therefore, the creeks incise down into the Red Bluff becoming entrenched and restricted from meandering. Where the monocline crosses Big Chico Creek the faults are spaced out much further and do not have such a steepening effect (see Geology Map). Since Big Chico Creek’s entrance to the valley is at a gentler gradient than that of Deer and Mill Creeks, the Red Bluff Formation has been eroded away in most of the area around Chico. Having less downcutting, erosional force entering the valley Big Chico Creek did not experience as much of an entrenching effect from the Red Bluff Formation. Instead the creek meandered more and eventually eroded away a much larger surface area of the Red Bluff Formation. Also the simple fact that the mouth of Big Chico Creek is further east of the Sacramento River than Deer and Mill Creeks allows more distance for the suspended sediment to be dropped out, creating a large alluvial fan.

The alluvial fan formed at the mouth of the canyon where the gradient of the creek lessens, allowing for deposition of sediments.

Seen from the air the deposit looks like a fan with the apex at the mouth of the canyon. As the fan developed through time, existing channels were filled and abandoned as new channels were formed. At one time or another, Big Chico Creek has flowed through most parts of Chico. The alluvial fan formed by Big Chico Creek is composed of extremely fertile soils, and these soils are a major contributor to the development of the agricultural economy in the area.

As Big Chico Creek flows from the mountains toward the valley its gradient changes many times, coinciding with the specific type of geology it is flowing over. The hard rock sections of the metavolcanics and the Lovejoy Basalt result in more varied, steeper sections, with harsher drops and deeper pools being formed. In the softer rock of the Chico and Tuscan Formations the creek’s gradient is much more gentle, as its flow velocity is decreased, through its lateral dispersal of energy. Big Chico Creek is continually incising (eroding down), through the different layers, exposing them in the canyon walls. One can see an example of this process very clearly in Upper Bidwell Park.

Alluvial fans developed at the margins of a mountain range.
From Guyton, 1978

Mud and Rock Creeks have simpler geology. Being much smaller watersheds, results in lower flows and have less erosional force to cut down through the different layers. Therefore, are primarily made up of the Tuscan Formation. However, there is a small exposure of Lovejoy Basalt near Richardson Springs on Mud Creek, and portions of both the Lovejoy and the Chico Formation are exposed in Rock Creek. In addition, there is a small strip of “Cohasset Ridge Basalt” on the ridge that is younger and overlying the Tuscan.

Profile of canyon in upper Bidwell Park.
From Guyton, 1978


Big Chico Creek originates from a series of springs, which flow off of Colby Mountain come together to form a main channel at Chico Meadows. From Chico Meadows, below the human-made lake at Camp Lassen at about 4,400 feet elevation, Big Chico Creek is a free flowing stream, down to Five-mile dam in Bidwell Park. After leaving Chico Meadows the creek turns and flows in a westerly direction for a short stretch before its confluence with Cascade Creek, the first main tributary, at Soda Springs Campground. From here the creek turns to the southwest and begins to follow the valley to the north of Highway 32. Downstream of the Cascade Creek confluence to Upper Bidwell Park, Big Chico Creek has six primary tributaries: Little Smokey Creek, Nine-mile Creek, Big Bear Creek, Little Bear Creek, Campbell Creek, and Web Hollow (see Hydrology map).

Downstream of Web Hollow, which drains off the uppermost portion of Cohasset Ridge, the creek flows freely for 3-4 miles before reaching Bear Lake, a large plunge pool formed by a waterfall. In this area Musty Buck Ridge becomes the watershed divide to the northwest, splitting flows between Big Chico Creek and Mud Creek. About 1/3 of a mile above the Ponderosa Way bridge the creek has another significant waterfall which forms Higgins Hole, the generally agreed upon uppermost barrier to anadromous fish migration. The creek continues toward the valley passing just north of Forest Ranch in a deep, wide topped canyon before reaching Upper Bidwell Park. As Big Chico Creek enters Upper Bidwell Park, it assumes a pool and drop morphology, due to a steeper gradient. This area, referred to as Iron Canyon, is characterized by classic wildland swimming holes, such as Browns Hole, Salmon Hole, Bear Hole, and other unnamed holes (see Hydrology map).

Bear Lake

Higgin's Hole

These holes may also serve as over-summering grounds for adult spring-run Chinook salmon, especially during drought years. Just below Browns Hole, above Salmon Hole, sits the Iron Canyon fish ladder. The ladder was built in the 1950’s to assist the salmon over a significant barrier on their journey upstream (Maslin, 1999). The only other fish ladder on the creek is located at One-Mile dam to assist the fish in passing over the dam.

At the Five-Mile dam, Big Chico Creek’s flow is partially diverted into Lindo Channel, or Sandy Gulch, as it was historically known. Lindo Channel is an ephemeral stream that formed as a natural channel on the Chico alluvial fan, but was historically modified for flood control purposes in the early 1960’s (Phipps, 1988). Lindo Channel runs parallel to Big Chico Creek for almost eight miles before rejoining the creek about 2.5 miles from Big Chico Creek’s confluence with the Sacramento River (see Hydrology Map). Lindo Channel is still used as a diversion channel to relieve flood flows in Big Chico Creek.

The channel carries water during the rainy season and is important for groundwater recharge as well as aquatic and riparian habitat. Another flood control channel, the Sycamore Diversion, was constructed off of Lindo Channel. It can be seen running to the northwest at the entrance to Upper Bidwell Park. This diversion brings flood flows off of Lindo Channel to Sycamore Creek, which drains into Mud Creek. Where Lindo Channel splits off at Five-Mile the flow capacity is 14,500 cubic feet per second (cfs), until the Sycamore Diversion split which is capable of receiving 8,500 cfs, leaving the rest of Lindo Channel with the design capacity of 6,000 cfs (U.S. Army Corp, 1961). These channels divert potentially damaging flood flows around the City of Chico. More hydrology information is available regarding the Big Chico Creek/Lindo Channel/Sycamore Diversion site and the One-Mile and Five-Mile facilities in Mitchell Swanson and Associates report for the City of Chico Parks Department (see bibliography).

Big Chico Creek enters the City of Chico flowing through Lower Bidwell Park and reaching One-Mile dam just east of the Vallombrosa and Mangrove/Pine intersection. One-Mile dam creates the Sycamore Swimming Pool; a public recreational area commonly referred to as One-Mile pool. The creek then flows directly through the California State University, Chico campus, providing a living laboratory for research at the University. The banks of the creek as it runs through the City of Chico remain in a relatively natural state with few cemented or rocked sections. There are two stream-flow gauging stations located on Big Chico Creek; one is located at Bidwell Golf Course and the other at the Rose Avenue bridge. The golf course station was a U.S.G.S. station from 1931 to 1986, when it was abandoned. It was not in use again until 1997 when it was moved downstream about ¾ of a mile and the Department of Water Resources (DWR) took it over its monitoring (see Appendix A for flow data).

After leaving Chico the creek continues to the west, passing through agricultural lands on its way toward the Sacramento River. Big Chico Creek has a levee running along its southeast bank from just above where Lindo Channel reenters, down to its confluence with the Sacramento River. About one mile from its confluence with the Sacramento River, Mud Creek joins Big Chico Creek (see Levee and FEMA Zone map).

As stated earlier, Mud Creek is a spring fed stream originating around 3,600 feet, draining off the south side of Cohasset Ridge and confined to the south by Musty Buck Ridge. The creek is perennial in most years down to where it meets Cohasset Highway. Mud Creek has two main tributaries, Maple and Cave Creeks, that originate at about 2,400 and 2,000 feet respectively, and both join Mud Creek near Richardson Springs. There are also many other springs in the area, some perennial and others intermittent that contribute water to Mud Creek. Moving downstream from its headwaters, Mud Creek has a series of small waterfalls located about one mile upstream of Richardson Springs. At Richardson Springs, at an elevation of about 600 feet, there is a 69-foot waterfall, which is the uppermost barrier to any fish migration. There is a group of mineral springs, which have a combined flow of approximately 15 gallons per minute in the vicinity of Richardson Springs (Chapla, 1973, Pg. 26). These springs are what brought development to Mud Creek Canyon in the late 1800’s. The springs are saline springs, and since the time the Indians occupied the area they have been known for their healing qualities. Above Richardson Springs there is a small diversion dam, which was used to divert water for domestic use as well as generate electricity. The diversion is no longer in use but the dam is still in place, holding back water in a small reservoir (Gallaway & Shellberg, 1996).

Downstream of Richardson Springs, Mud Creek flows to the west, passing just north of the Chico Airport. Just beyond the airport, the creek becomes restricted between levees, on the westside to the confluence with Rock Creek, via Kusal Slough, about one mile from where it joins Big Chico Creek. On the eastside the levee reaches to about a 1/5 of a mile from Big Chico Creek. Sycamore Creek flows just to the south of the airport and joins Mud Creek approximately 1/5 of a mile before it passes under Highway 99. Sycamore Creek is also restricted by levees from the confluence with Mud Creek upstream to just above Cohasset Highway (see Levee & FEMA Zone map). The Sycamore Creek diversion channel, which receives water from Big Chico Creek, has eroded away a great deal of material within its channel. This material has been transported down the system and formed depositional areas near Cohasset Highway and Meridian Road. There is one stream flow gauge located on Mud Creek just downstream of the Highway 99 Bridge (see Appendix B for flow data).

Flood Frequencies.
From Mitchell Swanson & Associates, p 32. 1994

Rock Creek

Rock Creek flows off the north side of Cohasset Ridge, originating around 3,800 feet. The creek flows just north of Cohasset Ridge for about six miles to where Keefer Ridge spurs off Cohasset and forms the headwaters of the Anderson Fork to the east, at around 2,400 feet, and drains the bottom portion of Cohasset ridge.

Anderson Fork, the main tributary, flows along Cohasset Road down to the edge of the foothills and joins Rock Creek at approximately 425 feet elevation. Rock Creek forms the Tehama/Butte County line from near its headwaters downstream approximately 6-7 miles. There is one small diversion dam in the valley section of the creek, just upstream of the Anderson Fork confluence, which is in use from April to November. The lower valley section of the creek is heavily channelized to protect urban and agricultural lands (Gallaway & Shellberg, 1996). Recent development in the Rock Creek floodplain has led to significant flooding problems. These problems are currently under investigation by the Army Corp of Engineers and Butte County. Rock Creek formerly flowed out onto the valley floor and into a large marsh, somewhere near Nord, which most likely drained into Pine Creek (Maslin, 1999). Presently Rock Creek drains into the human made Kusal Slough, which delivers the water to Mud Creek, about one mile upstream of the confluence with Big Chico Creek. Currently there is no stream flow gauging station located on Rock Creek (Clements, 1999).

Rock Creek Falls.

Soils and Vegetation

The soils within the Big Chico Creek watershed have been formed over long periods of time, originating from their parent material, the existing geologic formations. These parent materials have been influenced by many different factors in the process of soil formation. The five soil forming factors are Time, Parent Material, Climate, Biota, and Topography.

The different types of soils that are formed in turn support different compositions of vegetation. The following are general soil and vegetation descriptions for different zones within the Big Chico Creek watershed, taken from information provided by the local Natural Resource Conservation Service office, which is currently conducting the Butte County Soil Survey (Conlin, June 23,1999). These descriptions are for ridge top characteristics only. The soil properties within canyons and along the creek can be very different and, due to their complexity, are not addressed in this section. Starting in the uppermost reach of the watershed the first soil zone covers the area from just above Colby Mountain down onto the flanks of the mountain. This area is characterized by moderately coarse soils, ranging from shallow to very deep. This area supports a mixed conifer forest, which is made up of ponderosa pine, sugar pine, incense cedar, Douglas fir, and some large stands of white fir. Due to the higher elevation, this region also supports some red fir. The next zone reaches down from Colby Mountain to near the confluence with Cascade Creek and over to Lomo, the turn off from Highway 32 to Butte Meadows. This area has moderately coarse through moderately fine soils ranging in depth from shallow to very deep. These soils also support a mixed conifer forest.

The next zone reaches down to near the Web Hollow confluence, essentially the top end of Cohasset Ridge, over to near the Platte Mountain lookout, near the CDF station on Highway 32. The soils here have texture ranging from loamy through fine and can be shallow to very deep. A mixed conifer forest covers this area with smaller numbers of white fir.

The next region covers down to about 3,000 feet on Cohasset Ridge and around 2,000 feet along Highway 32 below Forest Ranch. The soils here are loamy through fine texture and range from very shallow to deep. Ponderosa pines dominate this area, mixed with some Douglas fir, sugar pine, black oak. Manzanita and shrubs cover the harsher areas.

The next zone drops down to about 1,500 feet. The soils in this zone are classified as loamy through moderately fine texture and range from very shallow to moderately deep. In general they support black oak, grey pine, buckbrush, manzanita and associated shrubs, and a few ponderosa pine.

The next zone, which occurs a few hundred feet downslope, is characterized by loamy through moderately fine soils that range from very shallow to moderately deep. The general vegetation cover is made up of blue oak, grey pine, buckbrush, manzanita and associated shrubs.

The final zone, which covers down to the confluence with the Sacramento River, could actually be split into several different regions but for the ease of description will be lumped into two sections. The foothill section of this zone, reaching down to about 500 feet near Horseshoe Lake in Upper Bidwell Park, is comprised of loamy textured soils that range from shallow to very shallow. These soils support blue oak and large expanses of grasslands, made up of various annual grasses. These grasslands, which are void of trees, such as near the Highway 32/Bruce Road intersection, are shallow remnant terraces. There is also an occasional grey pine scattered around near streams and on the ridge tops. The bottom section of this zone is made up mostly of the Big Chico Creek alluvial fan and Sacramento River flood deposits. These soils can be very deep and are considered Class I agricultural soils, supporting varied orchard and row crops.

Once again these descriptions are very general and it should be recognized that there is more variability in the canyon settings. For example in the canyon from Forest Ranch down through Upper Bidwell Park, there are many fractures in the rocks that allow enough water to seep out to support various species of shrubs and small trees, which grow on the canyon walls. Also along the contacts of the different layers of geology water is seeping out resulting in linear stretches of vegetation.

For more information on the soils in the watershed please contact the Natural Resource Conservation Service Chico Soil Survey office, which is currently conducting the new Butte County Soil Survey and has much more precise data available. The phone number is (530) 343-2731.

From almost 6,000 feet on Colby Mountain to 120 feet at the Sacramento River, Big Chico Creek watershed covers a diverse area. From dense stands of coniferous forest in the highest elevations to extremely fertile agricultural fields in the valley, the soils in the region, and the vegetation they support, are an important natural resource. Understanding the characteristics of the water from all the local springs, ranging from the healing waters of Richardson Springs to the clear, cool pools of Iron Canyon, is essential to planning for the health of the entire ecosystem. The geology of the area, which can be seen quite clearly in Upper Bidwell Park, gives a good insight to how the entire landscape within the watershed was formed. This simplified chapter on some of the physical characteristics of the watershed should provide a better overall understanding of the natural processes involved in forming the landscape we see today.

Data Gaps

  1. There is a flow gauge on the Chico State campus near the upstream side of campus that is not in use and could provide good data and could be monitored by University students and faculty.
  2. Currently there is no stream flow gauge located on Rock Creek. Due to the flooding concerns in this area, it would be beneficial to install a gauge on the creek.
  3. The potential ground water recharge through infiltration in the watershed is currently unknown and would benefit from further research.
  4. The changes in the movement of bedload materials in relation to the flood control structures around Chico have not been thoroughly examined, especially the lack of gravel recruitment in Lindo Channel and Big Chico Creek over the last few years.
  5. It also would be beneficial to have more knowledge of gravel movement and storage in the upper part of the watershed, focusing mostly on the tributaries and the Minnehaha Mine site.
  6. The effects of channel incision in Lindo Channel and the Sycamore Diversion channels are points of interest that could be studied further.
  7. On the smaller drainages of Mud and Rock Creeks, the effects of undersized culverts, acting like dams and barriers to fish passage, should be studied.
  8. The Butte County Soil Survey is currently in progress and when completed will be a much more thorough resource about soil conditions in Butte County.
  9. The effects of expanding impervious surfaces, which come with new development, on flooding needs further research.
  10. Since there is only one precipitation gauge located within the watershed it would be helpful to add a couple others to gather more data.


Chapla, Patricia Louise. (1973). Mud Creek Canyon: The Effect of Mineral Springs on Sequent Occupance in the Sierra-Cascadian Foothills. California State University, Chico, Masters Thesis.

Clements, John. (1999, June 21). Senior Engineer, Department of Water Resources. Personal Communication.

Conlin, Andrew. (1999, June 20). Soil Scientist, Natural Resource Conservation Service. Personal Communication.

Critchfield, Howard J. (1974). General Climatology, Third Edition. Prentice-Hall Inc., Englewood Cliffs, New Jersey.

Gallaway, Jody and Jeff Shellberg. (1996). An Investigation of Rock and Mud Creek in Butte County California. Class Project for Dr. Paul Maslin, Department of Biology, California State University, Chico.

Guyton, J. William and Frank L DeCourten. (1978). Introduction to the Geology of Bidwell Park. California State University, Chico, Department of Geological and Physical Sciences. University Foundation, California State University, Chico.

Maslin, Paul. (1999 June 17). Professor of Biology, California State University, Chico. Personal Communication.

Mitchell Swanson and Associates. (1994). Hydrology Management Plan for Big Chico Creek, One- and Five- Mile Dam Facilities and Lindo Channel. Prepared for City of Chico Parks Department. Sacramento, California.

Phipps, William Harrison. (1988). A Low Flow Analysis of Lindo Channel Regarding Anadromous Salmonids. California State University, Chico, Masters Thesis.

U.S. Army Corps of Engineers. (1961). Chico and Mud Creeks and Sandy Gulch General Design. Design Memorandum No. 5 Sacramento River and Major and Minor Tributaries, California. Sacramento, California.

The following maps were used in doing the research for this chapter:

California Department of Conservation, Division of Mines and Geology. (1992). Geologic Map of the Chico Quadrangle. 1:250,000.

California Department of Conservation, Division of Mines and Geology. (1977). Geologic Map of California. 1:750,000.

California Department of Natural Resources, Division of Mines. (1960). Geologic Map of California, Westwood Sheet. 1:250,000.

U.S.G.S. 7.5 Minute Series Quadrangle Maps — Butte Meadows, Onion Butte, Campbell Mound, Paradise West, Cohasset, Richardson Springs, Nord, Ord Ferry.

U.S.G.S. (1981). Geologic Map of the Chico Monocline and Northeastern Part of the Sacramento Valley, California. 1:62, 500




Soil Types


Levee & FEMA Zone Map

Average Rainfall