HR: 1340h
AN: GC33A-1243    [Abstracts]
TI: Paleoflood Hydrology and its Contribution in Interpreting the Effects of Climate Change on the Magnitude of Flooding in Mountain Ecosystems
AU: * Jarrett, R D
EM: rjarrett@usgs.gov
AF: U.S. Geological Survey, PO Box 25046, MS 412, Denver, CO 80225 United States
AB: Climatic conditions naturally vary over time; however, there is growing concern that anthropogenic effects also have influenced climatic variability. Substantial modeling has been done to assess the potential effects of assumed future climate change on mean annual temperature, precipitation, and streamflow. However, there has been little research related to the effects of climate change on extreme flooding. One approach to help understand and anticipate effects of climate change on the magnitude and frequency of future flooding is to document and analyze evidence of paleofloods preserved in mountain riverine ecosystems. Paleoflood hydrology is the study of flood-deposited sediments and botanical evidence preserved in rivers and their floodplains. Paleoflood data provide a means of assessing maximum floods and their ages associated with Holocene climates. This presentation compares contemporary flood data (historical and systematic streamflow-gaging station records) and Holocene paleoflood data in four distinct mountain ecosystem regions in the western United States. For each regional study area, envelope curves (graph of flood discharge versus drainage-area size with a maximum enveloping curve) defining maximum flooding were developed for contemporary and paleoflood data. These envelope curves of maximum contemporary floods and paleofloods were used to infer the effects of climatic variability on Holocene flood magnitude. The paleoflood envelope curves are slightly larger than the envelope curves of contemporary floods and differ between the mountain ecosystems; most likely, the differences stem from each ecosystem's hydroclimatic characteristics. Generally the difference between maximum contemporary and paleoflood magnitudes in each ecosystem are within the measurement error (about 10 to 30 percent) associated with the methods used to estimate flood magnitude. Thus, differences in climate and watershed conditions across the range of Holocene climates appear to have had relatively minor effects on flood magnitude in the mountain ecosystems investigated.
DE: 1130 Geomorphological geochronology
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1637 Regional climate change
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1821 Floods
SC: Global Climate Change [GC]
MN: Fall Meeting 2005