Bridges are a vital component of the transportation network. Evaluating their stability and structural response after a flood event is critical to highway safety. Bridge studies are usually designed with an assumption of an open channel flow condition, but the flow regime can switch to pressure flow when the downstream edge of a bridge deck is partially or totally submerged during a large flood. Figure 1 shows a bridge undergoing partially submerged flow in Salt Creek, NE, in June 2008. Figure 2 shows a totally submerged flow in Cedar River, IA, in June 2008, which interrupted traffic on...

Storm drains generally collect storm runoff from streets, parking lots, and other structures and convey this water to a desired outfall. Access holes (or manholes), which allow staff to inspect, maintain, or repair a segment of the drainage, are usually spaced about 92 to 183 meters (m) (300 to 600 feet (ft)) apart along a given pipe and at every junction between multiple pipes. An access hole, which has at least one inlet pipe and one outlet pipe intersecting it, is usually constructed from a vertically oriented concrete pipe or box that is large enough for a person to enter by removing the...

Bottomless culverts are three-sided structures that use the natural channel for the bottom. These structures could be used to convey flows from one side of a highway to the other. As such, they are an environmentally attractive alternative to box, pipe, and pipe arch culvert designs. Bottomless culverts range in size from less than a meter (1.5 feet) to more than 10 meters (35 feet) in width. The failure of such a structure could have severe consequences similar to the failure of a bridge. On the other hand, since the cost of the foundation and scour countermeasures represents a significant...

Bottomless (or three-sided) culverts use the natural channel bed and are environmentally attractive alternatives to traditional closed culverts. Moreover, they are considered by many highway agencies to be economical alternatives for replacing short bridges. They are typically placed on spread footings, and the issue of scour and the depth of footing must be addressed. The scour problem is analogous to abutment and contraction scour in a bridge opening and can be treated in much the same manner. Since abutment scour estimates at bridge openings are often quite large, a scour protection task...

Bridge piers and highway embankments leading to a bridge often obstruct the flow of floodwaters, causing an increase in velocity and the development of vortices. The increased velocity and vortices often cause scour near the bridge foundations. The damage to and failure of bridges caused by scour are problems of national concern. This report describes the results of the second USGS national field-data collection and analysis study on scour at bridges, funded by FHWA. The database originally developed during the first national study has been enhanced and many scour measurements added,...

This report presents the summary and synthesis of the various components of the experimental study entitled "Effects of Gradation and Cohesion on Bridge Scour" conducted at Colorado State University between the dates 1991 through 1996. As a result of this effort, in excess of 250 new pier scour data was collected and a new equation was developed expressing pier scour in terms of the dimensionless excess velocity factor, flow depth, pier diameter and a correction factor for the coarse fractions present in mixtures was derived. The new method was tested with available data from previous...

Durability of Culverts and Special Coatings is intended to provide up-to-date storm drain and culvert material selection methods and techniques to assist the highway engineer in designing culverts. While the program was to consider a variety of materials, the predominant focus was on Aluminized Type 2 corrugated steel pipe (CSP) and its performance versus galvanized CSP. This report is divided into two main sections-field investigation and literature review. The field investigation presents the results of a field evaluation of 32 pipes and their performance relative to that reported in...

Hydraulics and scour hazards cause over half of the bridge failures in the United States and have been identified by State bridge authorities as one of the top issues in bridge design and maintenance. Current pier scour design in the United States is mainly based on the Colorado State University (CSU) equation, which is described in Hydraulic Engineering Circular No. 18 (HEC-18). A recent evaluation of bridge scour research indicated a need to change the current method because substantial advances have been made in understanding pier scour processes. The evaluation compared several methods...

The goal of bridge inspections is to assess the safety of bridges on a regular basis so that any deficiencies will be identified and corrected. Given the large number of bridges over water in any State, bridge inspectors must inspect the superstructure, substructure, and waterway of each bridge in a short amount of time. A typical range of time for bridge inspections is 15 minutes to 2 hours, depending on the complexity and condition of the bridge. A more detailed inspection might ensue if a deficiency is detected. In the case of waterways and erosion, a hydraulic engineer might visit the...

The South Dakota Department of Transportation (SDDOT) and the Federal Highway Administration (FHWA) collaborated on a research study to determine the effects of a number of inlet geometry choices on culvert hydraulic efficiency. This study is a response to the large number of culverts that are installed in the United States and the fact that most of the current guidelines on culvert hydraulics are based on research completed more than 20 years ago. The objectives of this study were to: Determine optimum edge conditions for wingwalls; Determine the effects of inlet geometry on flow capacity of...