The Watershed

The Mattole watershed encompasses 304 square miles within the northern California Coast Mountains, some of the most rugged and geologically active land in California. The Mattole River flows completely un-dammed for 62 miles fed by over 74 tributary streams, from northern Mendocino County to its mouth at the Pacific Ocean, 10 miles south of Cape Mendocino.

The river and its tributaries provide important habitat for three salmonid fish species: steelhead trout, Coho (silver) salmon and Chinook (king) salmon.

The Mattole River, is in a extremely geologically active and unstable watershed, and is choked with sediment, which reduces its capacity to support fish and other aquatic organisms. Before wide scale timber harvesting, erosion happened slowly over thousands of years, and the river could transport sediment at a rate roughly equal to input of new sediment.

From the1940s to the 1970s, intensive timber harvest and other land use changes created hundreds of miles of poorly built roads. Combined with the floods of 1955 and 1964, many deep pools that used to exist in the river filled in, and the river channel became flatter and wider.

These changes have redefined the geomorphology of the river.  In response, the Council initiated the Good Roads, Clear Creeks Program in 2001 to assist landowners with sediment reduction. Based on the recommendations in the Council's 1989 report "Elements of Recovery," this is our primary strategy for assisting the river return to its pre-timber harvest condition.


Mattole Forests


The Mattole River watershed is largely a forested landscape, with several different forest ecotypes present: redwood, Douglas fir, mixed hardwood, oak woodlands, Sitka spruce, tanoak, and mixed conifers.

Some of the dominant hardwood trees include California Buckeye (Aesculus californica), Oregon White Oak (Quercus garryana), several Live Oaks (Quercus spp.), Pepperwood (Umbellularia californica), Tanoak (Lithocarpus densiflorus), Madrone (Arbutus menziesii), and, in riparian areas, Red Alder (Alnus rubra), Oregon Ash (Fraxinus latifolia), Elderberry (Sambucus spp.), Bigleaf Maple (Acer macrophyllum), Vine Maple (Acer circinatum), Dogwood (Cornus spp.), and several species of Willow (Salix spp.).


While the forests of the Mattole are diverse, three species stand out in the economic history of the place: tan oak, Douglas fir, and coastal redwood. The bark of tan oak was harvested in the late 19th century for its high tannin content. Tannic acid was necessary in the process of leather making. Most if not all of the harvested material was taken out by ship, from the mouth of the river near Petrolia.

Right: Tan bark piles before export from Petrolia in 1907. Photo courtesy of the Mattole Valley Historical Society.


An alder forest grows streamside. Photo: Amanda MalacheskyRiparian forests, those that grow along creeks and the River, are important to fisheries and riverine health as well. A healthy riparian canopy shades the watercourse and maintains cool water temperatures. In many coastal rivers, summertime water temperatures approach levels high enough to be lethal to salmonid fishes. Riparian zones act as a "buffer" between upslope lands and the river. This can work to prevent excessive nutrients and sediment from entering watercourses. Riparian vegetation also "armors" stream banks so that they can withstand high stream flows lessening the chance of eroding the banks. Fallen riparian vegetation (particularly the larger and more rot-resistant conifers) also contribute large woody debris to the river, which is important in the creation of complex habitats preferred by young salmonids.


In the Pacific Northwest of the 20th century, particularly in the post-World War II construction boom, harvest of redwood and Douglas fir has become economically important. Douglas fir is the dominant forest species in the Mattole watershed. Prior to World War II, the technology did not exist to make harvesting and transporting of logs out of the extremely steep and rugged country of the Mattole profitable. After the war, two conditions were in place to make logging of Douglas fir in the Mattole a reality: a standing-timber tax that made it economically difficult for private landowners NOT to cut trees, and the tank tread technology and heavy equipment needed to make roads and transport logs out.

From the time of the migration of Eastern settlers to the watershed, land in the Mattole was held in large tracts primarily for ranching and orchard agriculture. The standing-timber tax forced much of the ranching community to either log their land or lose it. In 1957, Humboldt County had more sawmills than any other county in the United States. So many logs were being transported out of the Mattole that log truck drivers had to time their trips to the mill as to avoid congestion on the small roads. In the 1980s, most of the original forest had been entered for harvest, and very little ancient forest remained.

In 1988, the Mattole Restoration Council created a map depicting the ancient forest cover in 1942 and in 1988. Below is a picture depicting old growth forests as of 1997, which shows that of the total Mattole forestlands, only about 9% remain as ancient forest. That percentage has since dropped to less than 8%. The MRC is actively engaged in efforts to preserve remaining old growth forests.

Mattole Geology


The Mattole watershed is located in one of the most geologically active spots in North America. Three tectonic plates meet offshore, the North American, the Gorda, and the Pacific, forming the Mendocino Triple Junction. This network of faults produces many earthquakes, including the large and devastating events of 1952 and 1992. To learn about recent earthquakes in the area, click here.

Rates of uplift in the King Range are among the highest anywhere in North America.

The Mattole watershed is underlain primarily by young sedimentary rocks, which are highly erodible and often incompetent - easily fragmented and cracked. Soils, which are primarily of the Atwell, Boomer, Cahto, Hugo, Josephine, Kneeland, Laughlin, Los Gatos, Mattole, Maymen, McMahon, Melbourne, Usal, Wilder and Zanone series, range in depth from less than a foot on rockier ridge tops to more than six feet in bottomlands.

Mattole Grasslands


Before Europeans arrived in California, grasslands looked very different then they do today. Perennial bunch grasses dominated grassland ecosystems. Bunch grasses can live up to 100 years, and are adapted to semi-arid summer conditions and geology that is unique to California ecosystems. Each year new shoots are formed out of a common fibrous root system. These bunch grasses, with their large and well-developed root systems, are excellent at holding soil on to hillsides.

Perennial grass species exist in patches in the Mattole, but have been largely supplanted by introduced annual grasses from Europe and Asia. Annual grasses complete their life cycle in one year. In the Mattole, this generally means winter and spring vegetative growth, followed by seed production in early summer. Annuals are essentially dormant through the driest parts of the late summer and fall. Because they die and dry up in the fall, annual grasslands pose a higher fire risk than perennial grasslands.

Research suggests that grasslands historically covered around 25% of the Mattole watershed. These grasslands are important economically, particularly for cattle and sheep ranching, and other agricultural operations.

Last year, the Mattole Restoration Council completed a project comparing the extent of grasslands in 1950 and 1998. According to this research, more than a third of the Mattole's grassland's have disappeared since 1950, primarily due to fire suppression which allows fir and brush to encroach on the prairie edges. To see the full report, look at centerfold of Newsletter #19.