- Email: [email protected]
Introduction to the special issue: Dams and geomorphology
Geomorphology 71 (2005) 1 – 2 www.elsevier.com/locate/geomorph
Preface
Introduction to the special issue: Dams and geomorphology 1. Introduction Dams profoundly impact the geomorphology of rivers by altering the natural patterns of water, sediment, and energy flow in those rivers. The over 75,000 dams in the continental United States alone are capable of impounding a volume of water almost equaling mean runoff for a year from that area (U.S. Army Corps of Engineers, 1996; Graf, 1999). These changes have a largely negative impact on aquatic and riparian ecosystems upstream and downstream of the dam. Natural dams also impact river geomorphology, although with positive and negative repercussions for aquatic and riparian organisms. Williams and Wolman (1984) summarize what was understood about the impact of dams on rivers at that time. Since then, significant research has expanded our understanding and influenced water resources policy in the United States and other countries. In 2002, the 33rd Binghamton Geomorphology Symposium convened under the theme bDams and Geomorphology,Q and featured invited papers and contributed posters on the topics of natural dams, artificial dams, and dam removal. This special issue includes 14 papers, representing approximately two-thirds of the oral papers and one invited paper based on an outstanding poster presentation.
2. Organization of this special issue This issue of Geomorphology is subdivided into three groups of papers. The first group provides a context for and review of our present understanding of the downstream effects of dams. Graf states that research on dams and geomorphology is both driven doi:10.1016/j.geomorph.2005.03.004
and limited by the human context, including policy, economics, and culture. Petts and Gurnell summarize the past 20 years of regulated river research, emphasizing the relationship between geomorphic change and ecological change in the riparian zone. The second set of papers examines the alteration of the flows of water and sediment, and consequent ecological changes, produced by dams. These eight papers show the range of spatial scales, countries, and concerns regarding the geomorphic impact of dams. Not all significant dams are human-made: natural dams, such as the beaver dams discussed by Butler and Malanson, can alter hydrologic and sedimentologic regimes to a similar degree. The paper by Magilligan and Nislow assesses changes in river regimes because of dams, observing that hydrologic alteration is not limited to large dams and large rivers, but shows consistency among a range of dam types and watershed areas. Marston, Mills, Wrazien, Bassett, and Splinter address the long-term effects of the Jackson Lake Dam on the Snake River and its floodplain in Grand Teton National Park, Wyoming. Renwick, Smith, Bartley, and Buddemeier also emphasize the significance of even small dams in their estimation of sedimentation in small, ubiquitous impoundments in the United States. Sedimentation behind dams is also a concern in Romania, as discussed by Ra˜doane and Ra˜doane. Alteration of water flow by dams also disrupts the flow of nutrients through riparian ecosystems, as demonstrated by Thoms, Southwell, and McGinness for the Macintyre River in Australia. The final two papers of this section delve into the drylands of the western United States, discussing channel adjustment following the construction of large dams on the Rio
2
Preface
Grande (Richard, Julien and Baird), the Green River (Grams and Schmidt). The final set papers address the impacts of the recent increase in the removal of dams for safety or environmental reasons. Dams and reservoirs have finite lifespans because of sedimentation in the reservoir, deterioration of dam materials, or obsolescence. The past few years has seen an increase in the number of dam removals, in part to remove structures that are likely to catastrophically fail without significant repairs and in part to allow for more natural flow regimes and for migratory fish passage. Geomorphologists study dam removal to understand the response of the fluvial system to the more natural flow regime and also to understand the fate of the sediment and, in many cases, contaminants stored behind the dam. Resources managers require such information to make appropriate decisions regarding the style of dam removal, goals of river restoration efforts, and pollution control. Two papers in this section address the fate of the sediment stored behind dams considered for removal, focusing on the potential threat to spawning habitats on Icicle Creek, Washington (Lorang and Aggett) and on the possibility of releasing toxic mercury from mining sediments on the Yuba River in California (James). Based on studies of several small dam removals in states in the upper Midwest, Doyle, Stanley, Orr, Selle, Sethi, and Harbor discuss the potential for ecosystem recovery following dam removal. Finally, Wildman and MacBroom present a case study the removal of two dams on the Naugatuck River in Connecticut as an evaluation of our understanding of channel change and ability to predict geomorphic change. By creating reliable water supplies, reducing damage and death as a result of flooding, and producing enormous amounts of electricity, dams have greatly benefited society, admittedly with an ecological cost. The impact of dams on landscapes will continue to stimulate geomorphologists to acquire knowledge of river processes, to predict river behavior, and to use the science of geomorphology in the realm of policy.
Acknowledgements The 2002 Binghamton International Geomorphology Symposium was held on October 12 and 13,
2002, on the campus of Bloomsburg University of Pennsylvania. Financial sponsorship for the meeting came from the Department of Geography and Geosciences and the College of Science and Technology at Bloomsburg University of Pennsylvania. I would like to extend my appreciation to Sandra L. Clark, Bridgewater State College, for assistance with the logistics of running the Symposium, and to Duane D. Braun, Bloomsburg University of Pennsylvania, for hosting a field trip in conjunction with the event. I offer a special thanks to the many individuals who willingly gave their time and energy in reviewing the papers for this special issue: Anne Chin, Texas A and M University; Mark Fonstad, Texas State University; Gordon Grant, USDA Forest Service; Jon Harbor, Purdue University; Carol Harden, University of Tennessee; Scott Lecce, East Carolina University; Frank Magilligan, Dartmouth College; Andrew Marcus, University of Oregon; Patricia McDowell, University of Oregon; Bob Pavlowsky, Southwest Missouri State University; Jonathan Phillips, University of Kentucky; Bruce Rhoads, University of Illinois Urbana–Champaign; Michael Slattery, Texas Christian University; and M C Thoms, University of Canberra. Finally, I am most indebted to North American Editor Dick Marston, David Butler, and Jack Vitek, who each spent many hours reviewing and editing these papers, and supporting the efforts of a junior faculty member early in her career.
References Graf, William L., 1999. Dam nation: a geographic census of American dams and their large-scale hydrologic impacts. Water Resources Research 35 (4), 1306 – 1311. U. S. Army Corps of Engineers. 1996. Water Control Infrastructure: National Inventory of Dams. [CD-ROM]. Federal Emergency Management Agency. Washington, D. C. Williams, G.P., Wolman, M.G., 1984. Effects of dams and reservoirs on surface-water hydrology: changes in rivers downstream from dams. U.S. Geological Survey Professional Paper 1286 (83 pp.).
Patricia J. Beyer Department of Geography and Geosciences, Bloomsburg University of Pennsylvania, 400 E. Second Street, Bloomsburg, PA 17815, USA E-mail address: [email protected].
Preface
Introduction to the special issue: Dams and geomorphology 1. Introduction Dams profoundly impact the geomorphology of rivers by altering the natural patterns of water, sediment, and energy flow in those rivers. The over 75,000 dams in the continental United States alone are capable of impounding a volume of water almost equaling mean runoff for a year from that area (U.S. Army Corps of Engineers, 1996; Graf, 1999). These changes have a largely negative impact on aquatic and riparian ecosystems upstream and downstream of the dam. Natural dams also impact river geomorphology, although with positive and negative repercussions for aquatic and riparian organisms. Williams and Wolman (1984) summarize what was understood about the impact of dams on rivers at that time. Since then, significant research has expanded our understanding and influenced water resources policy in the United States and other countries. In 2002, the 33rd Binghamton Geomorphology Symposium convened under the theme bDams and Geomorphology,Q and featured invited papers and contributed posters on the topics of natural dams, artificial dams, and dam removal. This special issue includes 14 papers, representing approximately two-thirds of the oral papers and one invited paper based on an outstanding poster presentation.
2. Organization of this special issue This issue of Geomorphology is subdivided into three groups of papers. The first group provides a context for and review of our present understanding of the downstream effects of dams. Graf states that research on dams and geomorphology is both driven doi:10.1016/j.geomorph.2005.03.004
and limited by the human context, including policy, economics, and culture. Petts and Gurnell summarize the past 20 years of regulated river research, emphasizing the relationship between geomorphic change and ecological change in the riparian zone. The second set of papers examines the alteration of the flows of water and sediment, and consequent ecological changes, produced by dams. These eight papers show the range of spatial scales, countries, and concerns regarding the geomorphic impact of dams. Not all significant dams are human-made: natural dams, such as the beaver dams discussed by Butler and Malanson, can alter hydrologic and sedimentologic regimes to a similar degree. The paper by Magilligan and Nislow assesses changes in river regimes because of dams, observing that hydrologic alteration is not limited to large dams and large rivers, but shows consistency among a range of dam types and watershed areas. Marston, Mills, Wrazien, Bassett, and Splinter address the long-term effects of the Jackson Lake Dam on the Snake River and its floodplain in Grand Teton National Park, Wyoming. Renwick, Smith, Bartley, and Buddemeier also emphasize the significance of even small dams in their estimation of sedimentation in small, ubiquitous impoundments in the United States. Sedimentation behind dams is also a concern in Romania, as discussed by Ra˜doane and Ra˜doane. Alteration of water flow by dams also disrupts the flow of nutrients through riparian ecosystems, as demonstrated by Thoms, Southwell, and McGinness for the Macintyre River in Australia. The final two papers of this section delve into the drylands of the western United States, discussing channel adjustment following the construction of large dams on the Rio
2
Preface
Grande (Richard, Julien and Baird), the Green River (Grams and Schmidt). The final set papers address the impacts of the recent increase in the removal of dams for safety or environmental reasons. Dams and reservoirs have finite lifespans because of sedimentation in the reservoir, deterioration of dam materials, or obsolescence. The past few years has seen an increase in the number of dam removals, in part to remove structures that are likely to catastrophically fail without significant repairs and in part to allow for more natural flow regimes and for migratory fish passage. Geomorphologists study dam removal to understand the response of the fluvial system to the more natural flow regime and also to understand the fate of the sediment and, in many cases, contaminants stored behind the dam. Resources managers require such information to make appropriate decisions regarding the style of dam removal, goals of river restoration efforts, and pollution control. Two papers in this section address the fate of the sediment stored behind dams considered for removal, focusing on the potential threat to spawning habitats on Icicle Creek, Washington (Lorang and Aggett) and on the possibility of releasing toxic mercury from mining sediments on the Yuba River in California (James). Based on studies of several small dam removals in states in the upper Midwest, Doyle, Stanley, Orr, Selle, Sethi, and Harbor discuss the potential for ecosystem recovery following dam removal. Finally, Wildman and MacBroom present a case study the removal of two dams on the Naugatuck River in Connecticut as an evaluation of our understanding of channel change and ability to predict geomorphic change. By creating reliable water supplies, reducing damage and death as a result of flooding, and producing enormous amounts of electricity, dams have greatly benefited society, admittedly with an ecological cost. The impact of dams on landscapes will continue to stimulate geomorphologists to acquire knowledge of river processes, to predict river behavior, and to use the science of geomorphology in the realm of policy.
Acknowledgements The 2002 Binghamton International Geomorphology Symposium was held on October 12 and 13,
2002, on the campus of Bloomsburg University of Pennsylvania. Financial sponsorship for the meeting came from the Department of Geography and Geosciences and the College of Science and Technology at Bloomsburg University of Pennsylvania. I would like to extend my appreciation to Sandra L. Clark, Bridgewater State College, for assistance with the logistics of running the Symposium, and to Duane D. Braun, Bloomsburg University of Pennsylvania, for hosting a field trip in conjunction with the event. I offer a special thanks to the many individuals who willingly gave their time and energy in reviewing the papers for this special issue: Anne Chin, Texas A and M University; Mark Fonstad, Texas State University; Gordon Grant, USDA Forest Service; Jon Harbor, Purdue University; Carol Harden, University of Tennessee; Scott Lecce, East Carolina University; Frank Magilligan, Dartmouth College; Andrew Marcus, University of Oregon; Patricia McDowell, University of Oregon; Bob Pavlowsky, Southwest Missouri State University; Jonathan Phillips, University of Kentucky; Bruce Rhoads, University of Illinois Urbana–Champaign; Michael Slattery, Texas Christian University; and M C Thoms, University of Canberra. Finally, I am most indebted to North American Editor Dick Marston, David Butler, and Jack Vitek, who each spent many hours reviewing and editing these papers, and supporting the efforts of a junior faculty member early in her career.
References Graf, William L., 1999. Dam nation: a geographic census of American dams and their large-scale hydrologic impacts. Water Resources Research 35 (4), 1306 – 1311. U. S. Army Corps of Engineers. 1996. Water Control Infrastructure: National Inventory of Dams. [CD-ROM]. Federal Emergency Management Agency. Washington, D. C. Williams, G.P., Wolman, M.G., 1984. Effects of dams and reservoirs on surface-water hydrology: changes in rivers downstream from dams. U.S. Geological Survey Professional Paper 1286 (83 pp.).
Patricia J. Beyer Department of Geography and Geosciences, Bloomsburg University of Pennsylvania, 400 E. Second Street, Bloomsburg, PA 17815, USA E-mail address: [email protected].