Browsing by Author "Lenhart, Christian"

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    Cost Analysis of Alternative Culvert Installation Practices in Minnesota
    (Minnesota Department of Transportation, 2009-06) Hansen, Brad; Nieber, John L.; Lenhart, Christian
    Various factors associated with conventional culvert design, including shallow water, perched inlets and high flow velocities, can cause difficulties for migrating fish and affect their genetic diversity and long-term survival. Conventional culvert design has traditionally been based on hydraulic conveyance, safety and cost. Recently, some alternative culvert designs have been developed to facilitate salmon migration on the west coat of the United States. These alternative designs focus on matching the natural dimensions and characteristics of the stream channel through the culvert. The intended purpose of these newer designs is to provide unimpeded passage of aquatic life, reduce maintenance costs and improve erosion control. Currently, some of these new designs are being implemented in Minnesota mostly when fish passage is a consideration. There are concerns about the additional costs associated with these alternative designs as well as whether they are really needed at some road crossings. The objectives of this research were to summarize state-wide fish passage concerns related to culvert road crossings on public waters and to perform a cost comparison between the conventional and the alternative culvert designs.
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    Evaluation of Buffer Width on Hydrologic Function, Water Quality, and Ecological Integrity of Wetlands
    (Minnesota Department of Transportation, 2011-02) Nieber, John L.; Arika, Caleb; Lenhart, Christian; Titov, Mikhail; Brooks, Kenneth N.
    Human activities including agricultural cultivation, forest harvesting, land development for residential housing, and development for manufacturing and industrial activities can impair the quality of water entering the wetland, thereby detrimentally affecting the natural ecological functions of the wetlands. This can lead to degradation of biota health and biodiversity within the wetland, reduced water quality in the wetland, and increased release of water quality degrading chemicals to receiving waters. Under natural conditions wetlands develop buffer areas that provide some protection from the natural processes occurring on adjacent areas of the landscape. Buffers serve the function of enhancing infiltration of surface runoff generated on adjacent areas, thereby promoting the retention of nutrients in the soil, and retention of sediment suspended in the runoff water, while still allowing runoff water to reach the wetland through subsurface flow routes. To protect wetlands and receiving waters downstream from the wetlands it is important that wetlands in areas disturbed by human activities be provided with sufficient buffer to prevent degradation of wetland biotic integrity as well as degradation of wetland water quality. The question arises, “How much buffer is sufficient?” The objective of this study was to investigate the sufficiency of buffers to protect wetland biotic integrity and water quality, and to evaluate the benefits extended to wildlife by the habit available in wetland buffers. The study was conducted by using a wetland data base available for 64 wetlands in the Twin Cities metro area.
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    Minnesota Guide for Stream Connectivity and Aquatic Organism Passage through Culverts
    (Minnesota Department of Transportation, 2019-01) Hernick, Matthew; Lenhart, Christian; Kozarek, Jessica; Nieber, John
    This guide assists Minnesota culvert designers in identifying, selecting, and implementing appropriate designs for maintaining aquatic organism passage (AOP) and stream connectivity at road-stream intersections. It was synthesized from existing literature and culvert design documents, a survey of Minnesota practitioners, research, and input from local, regional, and national experts. Culvert designs that create excessive velocity, physical barriers, or shallow depth can disrupt AOP and may be detrimental to the continuity of water flow, sediment, and debris transport vital to stream health. Conversely, the recommended culvert designs in this guide account for stream parameters such as slope and substrate that vary across Minnesota landscapes. A set of best practices captures critical design elements based on stream characteristics, which can be summarized as follows: 1.) Design the culvert to be similar to the stream channel (reference reach) by matching its slope, alignment, bankfull width, and flow depth to maximize AOP; 2.) Provide a continuous sediment bed with roughness similar to the channel, while maintaining continuity of sediment transport and debris passage, and; 3.) Design for public safety, longevity, and resilience. Culvert design that improves AOP and accounts for sediment transport is expected to reduce long-term maintenance costs and increase culvert life span.