Flood Risk Management and the American River Basin An Evaluation (1995) / Chapter Skim
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1 INTRODUCTION
1 INTRODUCTION
Pages 13-31
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This chapter provides a brief introduction to the American River basin for readers unfamiliar with the area and its need for flood protection. The first section provides background on the physical setting and historical context within in which any flood management policy in the area should be considered.
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The steep, west-facing slopes of the upper basin present an orographic barrier that extracts moisture from the prevailing maritime westerlies. Mean annual precipitation varies with elevation, forming a steep precipitation gradient from the Sacramento Valley up to the Sierra crest, from 18 to 70 in./yr, respectively (USAGE, Sacramento Districts, 1991, Appendix K)
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, but the area remained marshy, and a 1907 topographic map (California Debris Commission, 1907) represented the Natomas area as "Lake American." Historical Context of the Flood Control Controversy The Sacramento River has of course flooded since time immemorial.
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SOURCE: Sacramento District, USACE, 1991.
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i\ iSOUTH U ~ K E T ~ H O E Amok ' ~ ~ I Urn' ~ ALl t i r ~ / ~~ ~ _ ~ ~ $~\~ ~: S I L ~ ~ R r ~Or _'~ ~3) STA IE H I GH#AY ~ ~ I ~ TERSTATE H I GH.AY S -- - COUN TY BOUNDARY ~ AMERICAN RIVER ORAINAGL BASIN BOuNOARY ___ LO.ER RIVER FOLSOV RESERVOIR DRAINAGE SEPARAllON ~1 Main Features of the American River Watershed
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North Bloomington Gravel Mining Corp bans hydraulic mining Major flood destroys hydraulic mining infrastructure in mountains California Debris Commission created by Congress; small-scale, licensed hydraulic mining resumes 1894 Debate between "levees only" and combination approach continues 1905 Sacramento Drainage District established 1907 Great flood exceeding 600,000 cfs peak flow discredited "levees only" policy 1910 Jackson plan levees, bypasses, channel widening 1911 California Legislature adopts Jackson plan 1917 Federal Flood Control Act adopts Jackson plan 50-50 cost sharing 1935 Central Valley Project authorized by Congress 1956 Folsom Dam completed 1962 Lower American River Parkway established 1965 Auburn dam authorized by Congress 1975 Auburn dam construction suspended due to Oroville earthquake 1986 Major flood-nearly overtops downstream levees at Sacramento 1991 American River Watershed Investigation Feasibility Report published 1992 P.L. 102-396 authorizes Natomas elements and mandates this study 1993 NRC Committee on Flood Control Alternatives in the American River Basin formed 1994 American River Alternatives Report published Several long-standing issues continue to complicate present-day efforts to achieve safety from floods in the lower American River basin.
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Miners washed away overburden to reach gold-bearing gravel, thereby clogging stream channels with debris, endangering navigation, and aggravating flooding. Mining interests ex 2The definitive history of flood control in the Sacramento River basin is Robert Kelley's, Battling the Inland Sea: American Political Culture, Public Policy, and the Sacramento Valley 1850-1986.
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Nor was flood control planning integrated with other functions of water resources management until the 1930s. Gradually, as individual and collective landowners' flood control projects failed to stem the tide of flood damage and instead often shifted damage to other properties, more centralized institutions for flood management emerged.
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Congress provided 50 percent federal funding to implement it in the 1917 Flood Control Act. Except for the lower Mississippi River basin, this was the first federal financial participation in flood control project construction prior to the 1936 Flood Control Act.
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The Water Resources Development Act of 1986 expanded the nonfederal cost share for certain projects. The present situation on the lower American River is complex, with local interests that are acting through the Sacramento Area Flood Control Agency (SAFCA)
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Thus the estimated level of protection provided by Folsom Dam and downstream levees on the American River was revised downward from the 100-year event to about a 70-year event after the 1986 flood. (See Box 1.2 for an explanation of the term "100-year flood.")
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The proposed Auburn dam would have impounded runoff from the North and Middle Forks, controlling 973 square miles of the American River watershed and creating a two-pronged lake about 25 miles long. The originally proposed Auburn dam would have been another multipurpose structure, a concrete arch dam twice the height of Folsom (653 feet from base to crest)
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About one-third of a billion dollars was invested at the Auburn dam site and average maintenance costs for the site amount to $1.5 million annually (USAGE, Sacramento District, 1991~. Although the planned Auburn dam was redesigned to reduce seismic risk, the project as originally conceived lost support.
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THE USACE PROJECT PLANNING AND DECISIONMAKING PROCESS To have a full understanding of the American River flood control planning process, some familiarity with the USACE planning process in general is helpful. USACE studies for individual project planning move through a highly structured process that begins with a congressional study authorization, requires congressional and presidential approval, and ends (if successful)
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For example, prior to 1986 the beneficiaries of a local flood control project would be expected to provide only the lands, easements, and rights-of-way necessary for the proposed project to be implemented. A major flood control reservoir required no local contribution.
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of this planning process for the American River that provided the opportunity for critics to challenge the analysis of the Sacramento District and the plan preferred by the local sponsor. The fact that these challenges were made suggests that, although the process was open to inspection and comment after it was completed, it did not provide opportunity for significant, early input or fully incorporate the concerns of the interests who challenged the study.
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