Low water stream crossings in Iowa : a selection and design guide.

780073900PDFTech ReportStreamsFords (Hydrology)BridgesBridge designBridge constructionIowaIowa State University. Center for Transportation Research and EducationMcDonald, ThomasAnderson-Wilk, MarkIowa State University. Center for Transportation Research and EducationIowa. Highway Research BoardNTL-HIGHWAY/ROAD TRANSPORTATION-Bridges and StructuresUS Transportation CollectionMost Iowa counties maintain low volume roads with at least one bridge or culvert that is structurallydeficient or obsolete. In some counties the percentage of deficient drainage structures may be ashigh as 62%. Replacement with structures of similar size would require large capital expendituresthat many counties cannot afford. Low water stream crossings (LWSCs) may be an acceptable lowcostalternative in some cases.LWSCs are particularly suitable for low volume roads across streams where the normal volume offlow is relatively low. There are three common types of LWSCs:1. unvented fords2. vented fords3. low water bridges.LWSC sites, types, and designs should be carefully selected since low water stream crossings will beflooded periodically, requiring the road to be temporarily closed to traffic