HR: 1330h
AN: H52A-1167    [PDF]
TI: Historical Channel Change on the Upper Gila River, Arizona and New Mexico in Response to Anthropogenic Modifications and Extreme Floods
AU: * Klawon, J E
EM: jklawon@do.usbr.gov
AF: Bureau of Reclamation, P.O. Box 25007, Denver, CO 80225 United States
AU: Levish, D R
EM: dlevish@do.usbr.gov
AF: Bureau of Reclamation, P.O. Box 25007, Denver, CO 80225 United States
AB: Over the past century, the majority of alluvial reaches along the upper Gila River in Arizona and New Mexico have been leveed in an attempt to protect adjacent property from flood damage. In addition, the demand for irrigation has prompted the construction of diversion dams in these alluvial reaches to divert water for agriculture. Detailed geomorphic mapping and investigation of historical channel change along the upper Gila River reveals that many channel modifications are catalysts for major channel change and can result in catastrophic property loss rather than safeguarding valuable farmland. Channel widths were measured every kilometer for approximately 160 km from Safford Valley, Arizona through Cliff-Gila Valley, New Mexico for eight decades to develop a quantitative analysis of channel change. An overall pattern of channel narrowing and widening coincides with periods of few large floods and periods of multiple large floods, respectively. Furthermore, reaches along the upper Gila River with greater channel modifications have experienced more variation in channel width than reaches with fewer modifications. Although the average width of the upper Gila River is very similar to the width of the 1935 channel, the lateral position of the channel is very different in many reaches. Many channel changes in recent decades are unprecedented in previous historical aerial photography and reveal that the upper Gila River is currently eroding stream banks that are several hundred years to thousands of years old. These changes are consistently associated with artificial channel constrictions, such as levees, bank protection, and bridges, that have been built and rebuilt following large floods and that have accelerated natural channel narrowing during periods of few large floods. Examples of geomorphic responses due to channel modifications along the upper Gila River include lateral erosion upstream of levees and diversion dams, redirection of flow over diversion dams into opposite banks, breaching of levees during floods and resultant erosion behind levees, channel widening downstream of levees, aggradation in leveed reaches, and lateral migration associated with straightened tributary channels.
DE: 1803 Anthropogenic effects
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1860 Runoff and streamflow
SC: Hydrology [H]
MN: 2003 Fall Meeting