详情

Flood Hydrograph Generation for Predicting Bridge Scour in Cohesive Soils

项目名称：	Flood Hydrograph Generation for Predicting Bridge Scour in Cohesive Soils
摘要：	The method currently used by South Dakota Department of Transportation (SDDOT) for designing bridge foundation assumes that the bed material is sand and designs for a single (worst-case) flood event such as the 100-year or 500-year flood using the peak flow magnitude. Many bridges in South Dakota are founded on cohesive soils consisting of silts and clays (Niehus, 1996). Since silts and clays scour more slowly than sands, using the traditional methods for evaluating scour at bridges may over predict the extent of scour. This could result in over design of new bridge foundations or installation of unnecessary scour countermeasures at existing bridges. Furthermore, bridges that are classified as scour critical may in fact be safe. With reliable methods for predicting scour in cohesive soils, SDDOT could save significant time and money on bridges built over waterways. The Scour Rate In COhesive Soils (SRICOS) method (Briaud et al., 1999, 2001) is included in the current edition of Hydraulic Engineering Circular No. 18 (HEC-18; Arneson et al., 2012) as an alternative approach for predicting bridge scour in cohesive soils. The SRICOS method uses site-specific measurements of soil erosion rate to predict scour depth as a function of time. For soils that erode slowly, the final scour depth predicted by the SRICOS method could be significantly less than the equilibrium scour depth in sand. However, a hydrograph is required in order to use the SRICOS method. Various models have been developed by researchers to generate a continuous hydrograph over the design life of bridges (e.g., Brubaker et al., 2004; Brandimarte et al., 2006). These time series models require a great deal of effort to construct and are difficult to apply routinely by engineers. There is no guidance in HEC-18 on how to generate a hydrograph for using the SRICOS method. It is unclear what level of detail (e.g., a continuous hydrograph for multiple years with an annual flooding cycle, a series of design floods) is required in the temporal record of flows to correctly predict the final scour depth in cohesive soils. It is also unclear how to apply the SRICOS method to small watersheds and ungauged streams where historical flow records are lacking. SDDOT needs guidelines to define the site conditions in which the SRICOS method is more appropriate and more cost effective than the traditional methods, and to select a hydrograph generation method for using the SRICOS method.
状态：	Active
资金：	139672
资助组织：	Office of the Assistant Secretary for Research and Technology
管理组织：	Mountain-Plains Consortium
项目负责人：	Kline, Robin
执行机构：	Dept. of Civil and Environmental Engineering
主要研究人员：	Ting, Francis
开始时间：	20170328
预计完成日期：	20190930
实际结束时间：	0