Channel evolution of Des Moines Lobe till drainage ditches in southern Minnesota (USA)

摘要: Some drainage ditches in the intensively managed row-crop agricultural region of southern Minnesota evolved from a trapezoidal form to multi-staged channel forms similar natural streams. Older constructed cohesive sediment Des Moines Lobe till tend follow evolution model developed by Simon and Hupp. Site cross sections, longitudinal water bed profiles material particle size were determined according Harrelson others at 24 older ditch reaches, 5 newly reaches 13 stream reaches. Morphological features hypothesized change flat bench banks, benches found channels. All data statistically analyzed with respect area using regression, because is directly related for given climate, geology land use. Results show regression slope intercept bankfull width cross-sectional (CSA) streams compared typical designed ditches. Evolved small floodplain above adjusted their widths channels area. Old showed relatively strong R 2 (0.82, 0.68) CSA width, weaker (0.45) surface slope, little no correlation size. Channel appears have more quickly than facets and/or distribution. However, stepwise that D84, width/depth ratio mean depth explained 83 % variability across varying areas. Findings suggest possible reduction long-term maintenance costs if are allowed evolve over time. A stable typically self-sustaining, suggesting prior scheduled clean-out, should be examined hydraulic capacity, transport bank stability.