Geomorphic Responses to Interim Hydrology Following Phase Ⅰ of the Kissimmee River Restoration Project, Florida

摘要

Channelization of the Kissimmee River eliminated flow through the river channel, which allowed the formation of a largely organic deposition layer (ODL) on the river channel bed and stopped active sand transport needed to maintain point bars on meander bends. In 2001, completion of the first phase of dechannelization for the Kissimmee River Restoration Project (KRRP) reestablished flow to the river channel in the Phase Ⅰ area. This study evaluated changes in the ODL and the number of meander bends with active point bar development (MBPB) following Phase Ⅰ of dechannelization. Evaluations involved comparing interim measurements made after flow was reestablished to the river channel in the Phase Ⅰ area but before full completion of KRRP with (a) baseline measurements made before dechannelization and (b) predicted changes based on reference measurements representing the pre-channelization system. ODL thickness was measured in core samples on fixed transects perpendicular to the river channel. The ODL was thinner during the Interim Period than the Baseline Period and this decrease exceeded the expected change predicted from the reference condition. MBPB was assessed with aerial photography. MBPB increased from the baseline measurement of 0 bends to interim measurements of 27 bends in 2002 and 72 bends in 2009, approximating the increase predicted from the reference condition. The decrease in ODL thickness and the increase in MBPB to levels that meet or approximate the reference condition indicate that these aspects of the river channel are recovering following reestablishment of flow.