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Ecological Effects of the Lawn Lake Flood of 1982, Rocky Mountain National Park Scientific Monograph NPS/NRROMO/NRSM-93/2| United States Department of the Interior National Park Service The National Park Service pribliahes a ientific etudies of cignilix ant natural reacun es in unite of the National Park Syetem Thie reacarch ie of scholarly quality and may ime hede any die ipline of the biological physical or ccm ial ect enes Cover Photo A backdrop of mountains in Rocky Mountain National Park. Colorado, highlights the alluvial fan created by the Lawn Lake flood. Copies of this report are available from the Publications Coordinator, National Park en Box 25287, DenvCeO r80,225 . Cr Ecological Effects of the Lawn Lake Flood of 1982, Rocky Mountain National Park Editors HenryE .M cCutchen Northern Arizona University Cooperative Park Studies Unit Flagstaff, Arizona 86011 Raymond Herrmann National Park Service Colorado State University Water Resources Cooperative Park Studies Unit Fort Collins, Colorado 80523 David R. Stevens! Rocky Mountain National Park Estes Park, Colorado 80517 Scientific Monograph NPS/NRROMO/NRSM-93/21 United States Department of the Interior National Park Service +1993 ‘Present address: National Park Service Alaska Regional Office. Anchorage. Alaska 99503. ELAN PAGE Contents Hydraondl Geoomogrphyolo gy oft he1 982 Lawn Lake Dam Failure, Colorado, Robert D.J arraendt Jtoh n E Costa Geomorphic Response of the Fall River, Rocky Mountain National Park, Colorado, John Pitlick Alpine Sediment Movement and Erosion in the Roaring River Watershed, Rocky Mountain National Park. Rebecca M Summer Geochemistry of Iron Oxides in the Roaring River Alluvial Fan, Rocky Mountain National Park, Colorado.M /eey Litaor and RichardB . Keigley , Micronutrient Status of Tree Species Affected byt he Lawn Lake Flood in Rocky Mountain National Park, Colorado. KennethA . Barrick and Mark G. Noble... .. Vegetation Development on the Exposed Shores of Lawn Lake. Donald H Mansfield Macroinvertebrate Community Recovery Following Episodic Flooding — From an Earthen Dam Failure. DavidR . Beeansd Toerennce P.B oyle Terrestrial Arthropod Fauna of the Alluvial Fan Resulting From the Lawn Lake Flood. HowardE .E vans........ , Colonization of the Lawn Lake Alluvial Fan by Amphibians: Potential Effeof cBiottics a nd Abiotic Factors. LindaC .Z immermaann d PD + ch ctbseebeeseccecrecereseesepseecrecececs Changes in Avian Breeding Populations Resulting From the Lawn Lake Flood of 1982. RonaldA . Ryder and Deborah West Bangs |. . Effects of the Lawn Lake Flood on Local Distribution and Abundance of Mammals. David M. Armstrong ... 6.66 Observations of Plant Ecology on the Lawn Lake Flood Alluvial Fan. ED £6508650600000000005000000080000000080001 Foreword Lawn Lake is located at treeline, 3,450 m (10,987 feet) above sea level. It is in one of the Most scenic areofa Rsock y Mountain National Park, Colorado. In 1903, a privately constructed dam enlarged the lake to store water for irriga- tion, These activities preceded the designation of Rocky Mountain National Park in 1915, becofa thue esstabelish ed water rights, the dam continued to be privately managed, maintaining an easement within national park property. On 15 July 1982, the dam at Lawn Lake failed, probabldyu e to a piping failure. The subsequent flood sent approximately 831,000 m' of water cascad- ing down the Roaring River—causing the Caycade Lake Dam to fail—and then continuing through the town of Estes Park Three people were killed, and nearly $30 million of damage occurred. The president declared Larimer County a disaster area on 22 July 1982. Failure of the dam released a torrent that scoured the drainage of the Roaring River, inundated adjacent ecosystems, and deposited a large debris fan at the confluenofc eth e Roaring and Fall rivers in the park. The physical and biological effects of the flood were profound, particularly within the park. As perturbations of this type in high-elevation ecosystems are rare, the flood captured the interest of local, national, and international scientists and scholars, The period following the Lawn Lake Flood was recognized by the Na- tional Park Service (NPS) as a rare opportunity to study and better understand ecosafyfecsted tbye catmastsroph ic flooding. The present study represents the results of the last 8 years of multidisciprleisenarachr.y I n 1983, Gustav Swanson, professor emeritus of Colorado State University, focused the NPS effort when he proposed the concept of developing a research consortium for the flood. In May 1983, these thoughts became reality when the park hosted a meeting and field trip for interested invesFrotm tihat gfirsat mteetiong, rplasns r.api dly developed and were put in motion for the organization and funding of a multidisciplinary research effort to investigate the physical and biological effects of the flood as well as the area's subsequent recovery. The NPS Rocky Mountain Region and the NPS Water Resources Field Support Laboratory initiated the program. Later, addithelip owasn oabtalin ed from the National Park Service's Natural Resources Preservation Program. Contribuoft aiddoitniosna l value were made by other governmenatn d private sources. In addition, many of the contributors to this volume donated their professional skills and talents to these efforts. The result has been a multidisciplinary scientific study of an unusual event—a study that details many research efforts focused toward understanding the effects of and the response to the catastrophic flood on 15 July 1982. As their titles reflectt,h e 12 studies presented here have covered many physical and biological science disciplines, including geology. hydrology, chemis- try, botany, and zoology. The studies tell the story of the ecological changes iv that followed the failure of Lawn Lake Dam and the subsequent food that produced rapid hydrologic changes, including inundation, scouring and depo- sition (burial), nutrient and mineralogic changes, sediment accommodations, and direct biological effects. Finally, these studies detail the recovery processes that occurred in both aquatic and terrestrial biological communities, Many important publications on the effects of and the response to the flood were presebefnorte tehodse in this sympOones ofi theu mamjor, on es, published in 1986, is the 78-page U.S. Geological Survey Professional Paper by R. D. Jarrett and J, E, Costa titled Hydrology, Geomorphology and Dam- break Modeling of the July 15, 1982, Lawn Lake Dam and Cascade Lake Dam Failures, Larimer County, Colorado, Jarrett and Costa have provided a con- densed version of that monograph for this volume. A number of reports and publications have stemmed from the research of Dr. Colin Thorne (Queen Mary College, London, England) and his associates, This series of five reports, printed as technical reports of the NPS Water Resources Field Support Laboratory, are not reprinted in this volume because of space constraints, These reports include Bedload Transport and Hydraulic Geometry Relations for Fall River, Rocky Mountain National Park, Colorado (1984), by John P. Hick, Bed Material Analysis on the Fall River (1983), by David S. Biedenbain; two reports, Measurements of Bend Flow Hydraulics on the Fall River—at Low Stage (1983), and—at Bank Full Stage (1985), by Colin R. Thorne et al.; and Stream Discharge Rating Curves for the Fall River, Rocky Mountain National Park (1983), by Mark Segenthaler. Copies of these reports may be obtained from the U.S. Department of the Interior, National Park Service, Water Re- sources Division, Fort Collins, Colorado. Another article of interest can be found in the Journal of Sedimentary Petrology 57(\):1-18, titled Sedimentary Processes, Vertical Stratification Sequences, and Geomorphology of the Roar- ing River Alluvial Fan, Rocky Mountain National Park, Colorado, by Terence C. Blair. We again thank the authors and investigators who persisted —with mini- mal NPS help—to complete their studies. These studies represented a rare opportunity to learn more about a phenomenon of great importance to resources managers within the National Park Service and to land managers ev- erywhere. The results of their work have helped to better understthea nnatdur e of riparian changes that occur owning to catastrophic flood events and the recovery process that follows. James B. Thompson Superintendent, Rocky Mountain National Park The Editors Frontispiece. The alluvial fan that formed on the valley floor after the breaching of the Lawn Lake dam altered the appearance of the land scape and created a new lake (/ower left). The photo was taken in the summer of 1992. VY/ Hydrology and Geomorphology of the 1982 Lawn Lake Dam Failure, Colorado Robert D. Jarrett U.S. Geological Survey P.O. Box 25046, MS 418 Denver, Colorado 80225 JohnE . Costa U.S. Geological Survey 5400 MacArthur Boulevard Vancouver, Washington 9866] Abstract. Failure of the Lawn Lake Dam released 831,000 m' of water with an estimated peak discharge of 510 m'/s down the Roaring River valley. Floodwaters from Lawn Lake Dam overtopped a second dam with a peak discharge of 204 m'/s. Cascade Lake Dam, 10.8 km downstream, also failed and increased peak discharge to 453 m/s. Cascade Lake Dam, a 5.2-m-high concrete gravity dam with a capacity of 14,900 m', failed as 1.28 m of water flowed over its crest. The flood continued down the Fall River into the town of Estes Park. where it caused extensive damage. Peak discharge in the Big Thompson River at Estes Park was 156 m'/s. We present a summary of the dam failures, hydroalndo dgami-brcea k modeling analya dsisceusssio,n of the geomorphic effects of the flood, and an overview of the effects of the flood on the public. The documented 1982 flood indicates the need to improve the understanding of flood processes so that modeling dam-break floods in high-gradient rivers can be improved. These study results provide hydrologic, geomaond frloopd dahmagie icnfor,mati on for the assessment of floods from dam failures and baseline information for scientists conducting related research. Introduction / started to hear a sound like an airplane. Also, there were loud booms. It got louder and louder. 1 thought it was breaking the sound barrier. | kept looking for a plane but couldn't see one. 1 got suspicious and started looking upstream. | saw trees crashing over and a wall of water coming down. | started to run as fast as | could for high ground. There was a deafening roar. |f ell and got up and kept running. I stood on high ground and watched it wipe out our campsite. It knocked everything in its path over; Steve [his camping companion] didn't stand a chance. 2 R. D. Jannert ano J, BE. Costa With these words, Steven Cashman described his harrowing experience with the flood that swept his camping companion to his death in the Roaring River, Other campers along the Roaring River estimated the wall of water to be 8-10 m high, carrying with it large trees and boulders, so that the water looked like a wet, brown cloud that sounded like extremely loud continuous thunder, or a freight train, or an airplane breaking the sound barrier. After Cascade Lake Dam failed, two other campers were swept to their deaths a short distance downstream from the dam. The flood caused extensive damage to homes, businesses, and bridges, particularly in the town of Estes Park. Dave Thomas, observing the flood from a point 1.9 km upstream from Estes Park, indicated the floodwave “gradually began to swell—there was no wall of water.” In Estes Park, the flood entered the Big Thompson River for a short distance before being contained within Lake Estes by the U.S. Bureau of Reclamation's Olympus Dam, which is about 20 km downstream from Lawn Lake. Peak discharge into Lake Estes—156 m'/s—occurred about 3h 40 min after the failure of Lawn Lake Dam. In that brief time, three people were killed and approximately $31 million of total flood damage was incurred. Flood dam- ages included private and public property losses, debris cleanup, and eco- nomic losses to businesses in the Estes Park area. As a result of the flood, the president declared Larimer County a disaster area on 22 July 1982. The Lawn Lake Dam failure provided an opportunity to improve the understanding of hydraulic and geomorphic processes of large floods and their effect on stream channel morphology in mountainous areas. This paper pre- sents the setting, a summary of causes, effects on hydrology and geomorphology. and effects on the public of the dam failures and flood. Dam-break computer modeling was used to provide supplemental hydrologic information and to evaluate various hypothetical scenarios of dam-breach development and probable effects of the failure of Cascade Lake Dam. Documentation and analysis of the flood provide valuable information on the effects of floods from failure of small dams on high-gradient streams. This information can be used for future hazard mitigation related to dam failures and for studying the effects of floods from dam failures. Because the dam-failure flood occurred within National Park System lands, study of this flood enhanced the National Park Service (NPS) dam safety program and its relation to park resources. Setting Lawn Lake was an artificially enlarged natural lake occupying a moraine- dammed depression on the southeast side of the Mummy Range in Rocky Mountain National Park, Colorado (Fig. 1). The elevation of the lake is about 3,350 m. Local bedrock consists of Precambrian gneisses and schists that are more than 1.7 billion years old (Peterman et al. 1967). Lawn Lake is fed by the Roaring River, which originates at Crystal Lake, a tarn located about 1.6 km upstream at an elevation of about 3,500 m. Upstream from Lawn Lake, the