Process-Based Design Strengthens theAnalysis of Stream and Floodplain Systems under a Changing Climate

HighlightsStream-riparian interactions and preferential flow remain two “unsolved” problems in hydrology.Using mechanistic approaches enables analysis of stream and floodplain systems under future climatic extremes.Engineers should verify stream restoration designs with models that consider stream-riparian interactions.Riparian buffer design models should consider preferential flow and be more widely used for site-specific design. Keywords: . Climate Variability, Floodplain, Preferential flow, Process-based design, Riparian buffer, Stream restoration, Streambank erosion, Vegetative Filter Strip.

A Modeling Approach for Evaluating Watershed-scale Water Quality Benefits of Vegetative Filter Strip - A Case Study in Ontario

Vegetative filter strips (VFS) are globally recognized as an effective BMP in reducing non-point source pollution. Maximum effectiveness of a VFS at a watershed-level could be achieved by adequately installing and sizing a VFS along the edge of the field. Existing watershed models have limitations in appropriately representing and modeling VFS at the watershed scale. Therefore, in this research, a new modeling approach consisting of the Agricultural Non-Point Source (AGNPS) model, AGNPS_VFS toolkit, and a regression equation is developed to explore the effectiveness of VFS applied along the edge of fields. AGNPS cells are identified as locations where the edge of the field VFS is to be installed. Further, the approach was tested with a case study. The model was calibrated and validated for a flow and sediment load at the watershed outlet. Thereafter, the modeling approach is used to compute sediment reducing efficiency (SRE) for the edge of the field VFS. Objectives of this study were to test the effectiveness of uniform VFS (5 × 18 m) lengths located at several locations (draining an upstream area of 3, 4, 6 ha, and at spatially variable locations) within a watershed to demonstrate the ability of the developed approach to evaluate effectiveness of VFS application in sediment abatement. Maximum SRE was observed for VFS placed at spatially variable locations; the developed approach reduced nearly 23.03% of sediment yield, while VFS placed along cells draining an upstream area of 3, 4, and 6 ha removed 9.59%, 12.39%, and 5.91% of sediment loads respectively. Keywords: Non-point source pollution, Sediment transport, Vegetative filter strip (VFS), VFSMOD.

Design a Vegetative Filter Strips Length Using VFSMOD_W Model for Reducing Sediments and Pesticides

The vegetative filter strips (VFS) are a useful tool used for reducing the movement of sediment and pesticide in therivers. The filter strip’s soil can help in reducing the runoff volume by infiltration. However, the characteristics of VFS (i.e., length) are not recently identified depending on the estimation of VFS modeling performance. The aim of this research is to study these characteristics and determine acorrelation between filter strip length and percent reduction (trapping efficiency) for sediment, water, and pesticide. Two proposed pesticides(one has organic carbon sorption coefficient, Koc, of 147 L/kg which is more moveable than XXXX, and another one has a Koc of 2070 L/kg which is less moveable than XXXX) are presented, where the goal is to prevent 95% of incoming sediment and 85% of the incoming pesticide to reach a receiving stream in still water, Oklahoma from a cultivated field (1250 m²),for 2 hour storm with 5 years return period. Several VFS lengths were simulated including1, 3, 5, 6, 9, 11, 12, and 13 m. The results showed that the percent of reduction of sediment, pesticide, and water mainly depends on VFS lengths. Moreover, considering the design storms range, the simulation illustrated that the optimal filter length was13m for silty clay loam. When the value of was increased from 147 L/kg to 6070 L/kg, the filter length decreased from 13 to 9.5 because of the increase in trapping efficiency. In addition, the results revealed that the trap­ping efficiency was for sediment but not for water orpesticide which was highly impacted by the narrow filter strips. The amount of the rainfall and runoff of the designated field was larger than the infiltration capacity of filter strips, which resulted in low trapping efficiency for pesticide and water. Keywords: Models ,runoff, sediment, vegetative filter strip, , water quality, watershed planning.