Assessment of Management Strategies for a Straightened Lowland Agricultural Stream in Southwestern Québec
Abstract
Channel straightening and dredging were extensively used in the 20th century to improve agricultural fields' drainage efficiency and facilitate crop maintenance and harvest. Although the adverse geomorphologic and ecological effects of this practice on hydrologic networks are widely acknowledged, alternative management strategies remain marginal in Southwestern Québec. Furthermore, bank stabilization projects are often carried out to mitigate erosion at a local scale with little concern about the watershed scale, i.e. treating the symptom rather than the cause of erosion, and with little guidance on suitable designs for specific areas. We present here the results of a case study conducted in a small straightened agricultural stream in the St. Lawrence Lowlands (Richer stream, 45 km east of Montreal, Qc) to assess the efficiency of diverse instream structures to enhance bank stability. The loss in sinuosity and resultant increase in stream power in this stream resulted in acute erosion problems. A conceptual model developed in Java was developed to examine erosion processes at the watershed scale. This model is also used to parameterize a three-dimensional computational fluid dynamics model (Phoenics) to investigate the effects on flow field of employing various types of instream structures in a section of the Richer Stream which is particularly problematic for river management because of residential development and very limited space available for riparian zones. Model validation was achieved using flow velocity measurements obtained with an Acoustic Doppler Velocimeter. Simulation outcomes are analysed with regards to strategies using geomorphological, economical and ecological criteria in an attempt to identify their efficiency. The methods presented here can help decreasing the high degree of uncertainty generally involved in restoration activities by better assessing the efficiency of specific stabilization techniques prior to their implementation while considering unique stream/watershed characteristics and ecological factors.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2009
- Bibcode:
- 2009AGUSMCG21A..01R
- Keywords:
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- 1805 Computational hydrology;
- 1815 Erosion;
- 1825 Geomorphology: fluvial (1625);
- 1847 Modeling;
- 1860 Streamflow