Integrating Bioengineering and Geomorphology for Channel Stabilization and Enhancement

摘要

Erosion control along stream banks and channels has historically relied heavily on the use of hard structures, which are often over-designed and inconsistent with ecological objectives and functions. This is often still the case in urban, suburban and highly degraded environments. With the greater understanding of riparian functions and values that exist today, however, agencies and engineers are increasingly willing to implement alternatives to concrete and rock, even in constrained settings. Bioengineering techniques, which employ native species and natural materials in combination with hard structures, provide such an alternative. They do this by providing erosion control while restoring some natural riparian functions such as sediment trapping, runoff control, habitat creation and aesthetic enhancement. In order to ensure reliable, long-term protection, a bioengineering design requires careful analysis of hydrologic and geomorphic conditions. Basic principles of stable channel morphology should inform bioengineering projects, from the selection of materials, to the design of the channel form and cross-section, to the selection and appropriate location of vegetation and materials. In urban settings where erosion management and restoration measures are often undertaken on a piecemeal basis, the development of practical analysis and design methods based on sound geomorphic principles is critical. By integrating knowledge of native plant physioecology and fluvial morphologic conditions at a given site, reliable and self-sustaining erosion control solutions have been developed. Several case studies of planned and successfully implemented projects are presented. These cases demonstrate the integration of geomorphic considerations in bioengineering designs for erosion control in highly incised channels and situations where hard structures had originally been planned.