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Status assessment of agricultural drainage ditches

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2016 10th International Drainage Symposium Conference, 6-9 September 2016, Minneapolis, Minnesota  .(doi:10.13031/IDS.20162492397)
Authors:   Ingrid Wesström, Abraham Joel, Daniel Avilés
Keywords:   Cohesion strength, HEC-RAS, MADRAS, near saturation shear strength.

Abstract. Poor maintenance, environmental concerns, land use changes, and adaptation to climate change are creating a growing need for better agricultural drainage. The objectives of this study were to identify ditch properties that can be evaluated visually on-site and related soil erosion processes, and to define parameters requiring more intensive study and estimate these using simplified methods.

The study included surveys of ditches in various soils using MADRAS (Minnesota Agricultural Ditch Research Assessment for Stability) to classify the status of these ditches. To explain why some ditch sections were in poor condition, additional field and laboratory studies were carried out. Soil samples were taken for analysis of particle size distribution, near saturation shear strength (VJ Tech), and cohesion strength. The data model HEC-RAS was used for simulation of hydraulic forces acting at different flow rates. Digital maps of land use in the catchment area in different years were used to estimate changes in runoff conditions over time.

MADRAS proved to be a suitable tool for rapid assessment of stability problems in ditches. HEC-RAS simulations were a good complement to MADRAS in assessing how changes in land use affected the hydraulic load and in highlighting bottlenecks in systems. However, the hydraulic load did not adequately explain the degradation degree in some ditch sections. Measurements of soil shear strength were a good aid to understanding existing degradation. Thus assessment of sensitivity to erosion and bank failure are essential in anticipating the risks of future erosion processes in ditches.

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