during an average water year. In the 1960s, a dam for the Mad River in Humboldt County was proposed by the Army Corps of Engineers. The proposed blockage would have flooded the Maple Creek/Butler Valley area and adversely affected the health of the Mad River watershed. Gradually the opposition from the community, including the urban areas of the county, forced a suspension of the project schedule and finally the cancellation of the project. The dam was never built. The greatest problem of the Mad River drainage basin, as for many rivers in this area of the state, is erosion causing excessive sediment buildup in the river and its tributaries. The main causes of the erosion are excessive road building and logging, especially historical logging practices like clear-cutting. In addition, the removal of riparian vegetation (primarily due to conversion of natural lands to ranching purposes) increases erosion and urbanization causes decreased water quality. In 1992, the Environmental Protection Agency listed the Mad River under section 303(d) of the California Clean Water Act Section as sediment impaired, due to elevated erosion and siltation. In 2006, the river was additionally listed as temperature and turbidity-impaired. Land use The upper half of the river is inside the Six Rivers National Forest, but the vast majority of the river flows through private land, even in the national forest. About 64 percent of the land is used for timber production. Green Diamond is by far the largest landowner in the watershed, with about 42 percent of all land. The next largest landowners are R. Emmerson and Humboldt Redwood Company (formerly the Pacific Lumber Company), with 3 and 2 percent respectively. There are quite a few ranchers and lumber companies that own smaller, but still sizable, parcels. Private residences, open space and parks make up most of the rest. Ecology The river provides recreational opportunities and important habitat to fish and wildlife. Flora of the area includes the Mad River fleabane (Erigeron maniopotamicus), a wildflower which was named for the river. Key fish species include coho salmon (Oncorhynchus kisutch), Chinook salmon (O. tshawytscha), and steelhead (O. mykiss), which were federally-listed as threatened in the Mad River in 1997, 1999, and 2000, respectively. Two threatened osmerid species - longfin smelt (Spirinchus thaleichthy) and eulachon (Thaleichthys pacificus) - are also listed as present in the estuarine portion of the Mad River, but have not been observed in recent years.