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One of the major objectives in the design of the roadway drainage system is to limit the encroachment of the flow to that developed in the roadway drainage guidelines. However, this spread cannot be determined until the inlet is located. After the inlet is located, the drainage area contributing to the flow into that inlet […]

The roadway surface water can be removed by a series of drains that carry the water into a collection and disposal system. The curb, gutter, and inlet design must keep flooding within the parameters established in roadway drainage guidelines. The hydraulic efficiency of inlets is related to the roadway grade, the cross-grade, the inlet geometry, […]

Roadway drainage includes the entire system from pavement drainage through storm drains. Drainage features that make up the system include curbs, gutters, drop inlets, median drains, overside drains, roadside ditches, and storm drains. The basic design procedure for roadway drainage includes hydrology, surface water removal, and dis­posal. A properly designed system must adequately accommodate the […]

When the depth of flow is plotted against the specific energy, the specific energy diagram may be obtained and the critical depth found as illustrated in Fig. 5.5. The critical depth is defined as that depth where the specific energy is minimum. The flow velocity at the ШШїші HTDKAUlic graoe LINE channel bottom DATUM LINE […]

The energy equation is based on the principle that energy must be conserved; that is, the energy at any one cross-section on a stream is equivalent to the energy at any other section plus any intervening energy losses. This relationship, a form of the Bernoulli equation, may be used wherever there is a change in […]

The fundamental relationships for hydraulic flow are the same for channels that are physically open at the top, such as roadway channels and curbs and gutters, and for pipes and culverts that have a free water surface. In both cases, hydraulic design is based on open-channel flow. An understanding of these relationships is important for […]

Highways are often located adjacent to streams, lakes, and coastal areas. Channel and shore protection must be provided wherever the need is apparent or the risk is high. In other circumstances, where the possibility of damage to the roadway or adjacent land is not clear or risk is low, it may be acceptable to delay […]

At times it will be advantageous or necessary to realign or change the hydraulic char­acteristics of the channel. Reasons for altering the channel include improving culvert alignment, protecting roadways from erosion damage, reducing maintenance require­ments, and eliminating hydraulic structures where the roadway recrosses the channel. Plans for channel modifications must include a determination of what […]

As the name implies, open-channel flow is concerned with the conveyance of water with a free surface. This article primarily concerns lined and unlined channels such as encountered along roadways in highway design. 5.2.1 General Considerations The parameters to consider in choice of channel cross-section include hydraulics, safety, maintenance, economics, and the environment. These considerations […]

Many computer models have been developed for calculating rainfall runoff. Examples include the U. S. Army Corps of Engineers HEC-HMS model, the NRCS TR-20 model, and the FHWA-funded HYDRAIN system. As with all computer models, the accuracy and validity of the output can be only as accurate and valid as the input. The input and […]