Eel River Delta

Though the Delta of the Eel River extends to the junction with the Van Duzen River and the tidal influence is felt some 10 kilometers (6 miles) inland, the greatest diversity of habitats is found within a few kilometers of the mouth.

At least nine habitats are found here, riparian woodland, uplands, fresh and salt water marshes, tidal mudflats, shallow water bays and sloughs, deep-water channels, sand dunes, and sand and gravel bars. Most extensive are the riparian woodlands, which are found along much of the river and its tributaries. Alder, Alnus rubra, black cottonwood, Populus trichocarpa, and oak, Quercus sp., are dominants. In the uplands, which include some stabilized sand dunes, willow, Salix scouleriana, and coyote brush, Baccharis pilularis, are prominent.

There are about 280 hectares (700 acres) of salt marsh with cordgrass, Spartina foliosa, pickleweed, Salicornia ambigua [?], alkali bulrush, Scirpus robustus, and salt grass, Distichlis spicata. Two rare plants, Castilleja ambigua ssp. humboldtiensis and Cordylanthus maritimus ssp. palustris, are found in the vicinity.

The size of the freshwater marshes varies seasonally but averages 140 hectares (350 acres). These marshes are found primarily on the inland side of the dunes; bulrush, Scirpus criniger, sago pondweed, Potamogeton pectinatus, and widgeon grass, Ruppia maritima, are prominent here. On the sand dunes, particularly the higher and more stable, Lupinus sp., beach strawberry, Fragaria chiloensis, and sand verbena, Abronia latifolia, are among the many herbs observed.

Enteromorpha sp., Ulva sp., and other algae are found in the invertebrate-rich tidal mudflats.

Animal life is quite abundant, with over 40 species of mammals and 200 birds recorded here. Noteworthy among the mammals are the mountain beaver, Aplodontia rufa, and river otter, Lutra canadensis. Over half the birds sighted are water-associated species. Peak use is during the migratory season. There are several egret-heron rookeries in the area. The rare peregrine falcon, Falco peregrinus, once nested here but has not been sighted recently.

Several reptiles and amphibians are present; Pacific giant salamanders, Dicamptodon ensatus, are abundant. Thirty species of fresh, salt, brackish water or anadromous fish utilize the area for spawning, nursery or as a residence. The most common fish is the three-spine stickleback, Gasterosteus aculeatus. King and silver salmon, Oncorhynchus tshawytscha and Oncorhynchus kisutch, use the estuary as a nursery. The area is the southern limit for the coastal cutthroat trout, Salmo clarkii.

In the Mid to Upper Pleistocene, the Eel, Elk, Van Duzen and Mad Rivers drained into a single large bay. Table Bluff, formed through warpage, now separates the Eel from Humboldt Bay. The Delta is Quaternary and Recent alluvium, with typical meanders and small tributaries.

Integrity: Much of the former salt marshes have been filled for agricultural use; there are levees, buildings, roads, etc. As the Eel River Basin is the fastest eroding basin in the nation, sedimentation is a major threat to the Delta.

Use: Educational, research, observational, light recreational, in public areas; remainder, private.

Ref: Monroe, G. W. and F. Reynolds, 1974. Natural Resources of the Eel River Delta. Calif. Dept. of Fish and Game Coast. Wetland Ser. No. 9, 108 pp.

January 1976