HR: 11:00h
AN: NB22G-03    [Abstracts]
TI: Two case studies in river naturalization: planform migration and bank erosion control
AU: * Abad, J D
EM: abad@uiuc.edu
AF: Graduate Research Assistant. Dept. of Civil Engineering, University of Illinois at Urbana-Champaign, 205 N. Mathews Ave, Urbana, Il 61801 United States
AU: Guneralp, I
EM: iguneralp@uiuc.edu
AF: Graduate Research Assistant. Dept. of Geography, University of Illinois at Urbana-Champaign, 607 S. Mathews Ave, Urbana, Il 61801 United States
AU: Rhoads, B L
EM: brhoads@uiuc.edu
AF: Professor and Head of Dept. of Geography, University of Illinois at Urbana-Champaign, 607 S. Mathews Ave, Urbana, Il 61801 United States
AU: Garcia, M H
EM: mhgarcia@uiuc.edu
AF: Chester and Helen Siess Professor. Dept. of Civil Engineering, University of Illinois at Urbana-Champaign, 205 N. Mathews Ave, Urbana, Il 61801 United States
AB: A sound understanding of river planform evolution and bank erosion control, along with integration of expertise from several disciplines is required for the development of predictive models for river naturalization. Over the last few years, several methodologies have been presented for naturalization projects, from purely heuristic to more advanced methods. Since the time and space scales of concern in naturalization vary widely, there is a need for appropriate tools at a variety of time and space scales. This study presents two case studies at different scales. The first case study describes the prediction of river planform evolution for a remeandering project based on a simplified two-dimensional hydrodynamic model. The second case study describes the applicability of a Computational Fluid Dynamics (CFD) model for evaluating the effectiveness of bank-erosion control structures in individual meander bends. Understanding the hydrodynamic influence of control structures on flow through bends allows accurate prediction of depositional and erosional distribution patterns, resulting in better assessment on river planform stability, especially for the case of natural complex systems. The first case study introduces a mathematical model for evolution of meandering rivers that can be used in remeandering projects. In United States in particular, several rivers have been channelized in the past causing environmental and ecological problems. Following Newton's third law, "for every action, there is a reaction", naturalization techniques evolve as natural reactive solutions to channelization. This model (herein referred as RVR Meander) can be used as a stand-alone Windows application or as module in a Geographic Information System. The model was applied to the Poplar Creek re-meanderization project and used to evaluate re-meandering alternatives for an approximately 800-meter long reach of Poplar Creek that was straightened in 1938. The second case study describes a streambank protection project using bendway weirs. In the State of Illinois, bendway weirs constructed of rock have been installed at hundreds of sites, especially on small streams, to control streambank erosion. Bendway weirs are low hard structures installed in the concave bank of a meander bend. Design criteria for these weirs are approximate and have not been rigorously evaluated for overall effectiveness at low-, medium- and high flows. This initial step of the study attempted to describe the hydrodynamics around the weirs and the influence of the hydrodynamic patterns on sediment transport (near-field and far-field). To do that, a state-of-the-art three-dimensional CFD model was used to simulate flow through meander bends where 3D velocity measurements have been obtained to validate model predictions at low stages. Results indicate that the weirs produce highly complex patterns of flow around the weirs, which in some cases may actually increase erosional potential near the outer bank. These two case studies represent components of an emerging initiative to develop predictive tools for naturalization over a range of spatial and temporal scales
DE: 1824 Geomorphology (1625)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly