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REGULATED RIVERS: RESEARCH & MANAGEMENT, VOL. 11, 249-261 (1995) ENVIRONMENTAL CONSIDERATIONS FOR ASSESSING DAM REMOVAL ALTERNATIVES FOR RIVER RESTORATION JOHN R. SHUMAN St Johns River Water Management District, PO Box 1429, Palatka, FL 32178-1429, USA ABSTRACT Dam removal has received increasing attention over the last several years as a viable alternative to rehabilitation of unsafe dams and as an alternative for consideration as many hydroelectric dams come up for relicensing in the USA. The environmental impacts of dams on river ecosystems have been studied far more extensively than have the impacts of removing dams. Comprehensive environmental research is currently being conducted, assessing both the positive and negative impacts of the possible removal of Rodman Dam on the Ocklawaha River, Florida. The 2073 m long and 6.7 m high dam was constructed in 1968, impounding 3642 ha on this 125 km long river. The impacts of dam removal are com- pared with those expected by retaining and actively managing the reservoir for fish and wildlife. The research approach described here for addressing alternatives is recommended as a holistic procedure in which to make an environmentally based decision regarding dam removal. KEY WORDS: dam removal; reservoirs; dams; impact assessment; river restoration; Ocklawaha River; Florida; Rodman Dam INTRODUCTION Dams have long been viewed as more or less permanent fixtures on rivers, with only periodic maintenance required. Viewpoints are beginning to change, however, as some dams have been removed and others are proposed for removal. Both the Federal and State governments are involved in assessing the safety and fate of dams, with the Federal Energy Regulatory Commission (FERC) considering the establishment of a dam decommissioning policy. The FERC is now faced with decisions on the relicensing of 230 dams on 59 river basins. Dam removal may be a realistic alternative for some. There are over 75 000 dams in the USA, with the peak in dam-building having occurred during 1900-1949 (FEMA, 1993). Approximately 90% of the dams are owned by private entities or municipalities. State and Federal governments own approximately 7% of the dams. Texas and Kansas lead the nation in the number of dams, each with over 5 000 (Table I). Delaware, Hawaii, Alaska and Rhode Island all have fewer than 200 dams each. The primary purposes of most dams include recreation (31 %), fire protection and/or farm ponds (17%), flood control (14%), irrigation (14%), water supply (10%), and hydroelectric power generation (3%) (FEMA, 1993). As the national economic base has changed since the construction of many of these dams, their intended purposes have sometimes shifted or become less important. As the average age of dams in the USA is 40 years, many dams are in need of safety rehabilitation. Very often, the costs for rehabilitation are excessive for the 90% of dams owned by private owners or municipa- lities. Dam removal in these instances is often the only economically viable alternative. Most of the dams that have been purposefully removed (i.e. not including dam failures) in this country have been removed because they were too costly to rehabilitate. Examples of these include Salling Dam in Michigan and Woolen Mills Dam in Wisconsin. In the last few years there has been a concerted effort by environmentalists and others to recommend dam removal based solely on the environmental impacts of a dam on the river ecosystem. To date, most proposed removals have focused on dams having significant impacts on anadromous fish migrations. Probably the best known of these are the Elwha and Glines Canyon dams on the Elwha River in Washington and the Edwards Dam on the Kennebec River in Maine. Both dams significantly reduce salmon migrations in their rivers. CCC 0886-9375/95/070249-13 Received 15 July 1994 X, 1995 by John Wiley & Sons, Ltd. Accepted 17 January 1995