Northern California

Leslie Ewing, California Coastal Commission
Northern California: The region of Mendocino, Humboldt and Del Norte Counties
contain some of the most rugged and secluded portions of the California coast. The
landscape strongly influences the major industries, with timbering in the forest areas,
dairy in the valleys, fisheries in the streams, rivers and bays, and tourism throughout the
region. The coast is varied, but can be segmented into 3 large stretches.
Rugged cliffs, sea stacks, rocky shorelines, tide pools and small pocket beaches at the
mouths of streams and rivers characterize the Mendocino and southern Humboldt coasts.
There are large dune systems at Manchester State Beach and the pygmy forests at Jug
Handle State Reserve are on uplifted marine terraces. Most coastal development is
concentrated in the southern part Mendocino County, and in the region near the towns of
Mendocino, Noyo, Fort Bragg, Westport and Rockport. Gualala, in the southern region
has experienced severe erosion from a combination of wave action and landslides.
Further to the north, the main mechanisms for bluff retreat are rock falls, landslides and
groundwater induced slope failures. North of Fort Bragg and Westport, the main
highway takes an inland route. Most land is within the King Range National
Conservation Area and there are only a few paved roads to provide coastal access.
Eel and Mad Rivers and Humboldt Bay dominate the middle segment of the Northern
California. The Eel River has the highest ratio of sediment loading to watershed area of
any river in the lower 48 states. This coastal region has very high littoral transport rates
and comparably large sand supplies. Along with the segment to the north, it is frequently
exposed to large waves and violent storms. Much of this coastal region experiences
extensive bluff retreat from either wave attack or landsliding. Some areas, such as Big
Lagoon, north of Trinidad, have experienced 20 or 30 feet of bluff retreat from a single
storm. There are only a few areas where it is safe to develop adjacent to the coast, and
much of the development in areas like Big Lagoon is designed to be removed or relocated
to accommodate these large bluff losses. Despite the high erosion rates in this area, there
is pressure to increase development along the coast. Anther major concern for this area is
flooding. Sand barriers close many of the lagoons naturally. As development increases
around the lagoons, there are more frequent proposals to breach the lagoons artificially
and drop water levels around the lagoon. The Mad River is another concern for this
region. In the 1970’s the river began a northern migration that eventually stopped 3.4
miles to the north in 1991, at an engineered revetment that was installed to protect
Highway 101. During its migration, the Mad River carved out massive sand dunes,
exposing previously protected bluffs to wave attack. In 1999, the river returned to its
more southerly location, but its ambulatory nature may again expose these areas to
flooding and wave attack.
Two large sand spits protect Humboldt Bay and since the turn of the century, two jetties
have stabilized the entrance. For many years, there were just a few small communities
on the spits, and pulp and paper mills used most of the land. Recently several large
parcels have been purchased for private development and there are plans to establish
another community on the north spit. This area is exposed to severe winter storms and
wave attack. To date it has been fairly well protected by a well-established dune system.
However increased foot and vehicle traffic on the dunes, or a change in sediment supplies
could lead to dune deflation and greatly increase the risk of wave and storm attack. This
area is also at risk from tsunamis and due to limited road access, vertical evacuation may
be the only option for the spits.
Sand and cobble beaches backed by coastal bluffs with some more resistant rocky
promontories characterize the northernmost segment of this region, northern Humboldt
County and Del Norte County. Development has occurred mainly in a few coastal towns
such as Crescent City and Smith River. The coast and Highway 101 are at risk from
erosion and landslides. Crescent City experienced tsunamis in both 1960 and 1964.
Much of the downtown was damaged during the 1964 tsunami and a waterfront park now
replaces the first row of waterfront development. In the fall of 2002, Crescent City
became the first tsunami-ready community in California; nevertheless, tsunamis remain a
serious concern for coastal development in this community.