Laserfiche WebLink
<br />. A schedule for the timely design and construction of permanent scour <br />countermeasures or immediate bridge replacement depending on risk involved. <br />Monitoring can be an effective countermeasure to enhance public safety; <br />however, the use of monitoring does not "fix" the scour problem and the bridge <br />would still be considered scour critical until such time as permanent <br />countermeasures are installed. <br /> <br />3.3 Biological Countermeasures <br /> <br />A countermeasure group not included in the matrix is biological countermeasures such as <br />biotechnicallbioengineering stabilization. This group was not listed because it is not alS well <br />accepted as the classical engineering approaches to bridge stability. Bioengineering is a <br />relatively new field with respect to scour and stream instability at highway bridges. There is <br />research being conducted in this field, but bioengineering techniques have generally not <br />been tested specifically as a countermeasure to protect bridges in the riverine environment. <br /> <br />3.4 Countermeasure Characteristics <br /> <br />The countermeasure matrix (Table 1) was developed to identify distinctive characteristics for <br />each type of countermeasure. Five categories of countermeasure characteristics were <br />defined to aid in the selection and implementation of countermeasures: <br /> <br />. Functional Applications <br />. Suitable River Environment <br />. Maintenance <br />. Installation/Experience by State <br />. Design Guidelines Reference <br /> <br />These categories were used to answer the following questions: <br /> <br />. For what type of problem is the countermeasure applicable? <br /> <br />. In what type of river environment is the countermeasure best suited or, am there <br />river environments where the countermeasure will not perform well? <br /> <br />. What level of resources will need to be allocated for maintenance of the <br />countermeasure? <br /> <br />. What states or regions in the U.S. have experience with this countermeasure? <br /> <br />. Where do I obtain design guidance reference material? <br /> <br />3.4.1 Functional Applications <br /> <br />The functional applications category describes the type of scour or stream instability problem <br />for which the countermeasure is prescribed. The five main categories of functional <br />applications are local scour at abutments and piers, contraction scour, and vertical and <br />lateral instability. Vertical instability implies the long-term processes of aggradation or <br />degradation over relatively long river reaches, and lateral instability involves a long-term <br /> <br />6 <br />