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and HEC Number 13, Hvdraulic Desi2n of ImDroved Inlets for Culverts with other more recent culve.rt information devel- oped by governmental agencies, universi- ties, and culvert manufacturers to produce a comprehensive culvert design publica- tion. (1,2,3) HYDROLOGIC ANALYSIS SITE DATA AOUIS ITION CULVERT DESIGN DESIGN DOCUMENTATION TAPERED INLET DESIGN STORAGE ROUTING ANALYSIS Figure I-3--Culvert design procedure flowchart. B. Overview Of Culverts. A culvert is a hydraulically short conduit which conveys stream flow through ~ j j a roadway embankment or past some other type of flow obstruction. Culverts are constructed from a variety of materials and are available in many different shapes and configurations. Culvert selection factors include roadway profiles, channel characteristics, flood damage evaluations, construction and maintenance costs, and estimates of service life. 1. Shapes. Numerous cross-sectional shapes are available. The most commonly used shapes, depicted in figure 1-4, include circular, box (rectangular), elliptical, pipe-arch, and arch. The shape selection is based on the cost of construction, the limitation on upstream water surface elevation, roadway embank- ment height, and hydraulic performance. 1 I ~ i j i 1 1 ~ 2. Materials. The selection of a culvert material may depend upon structural strength, hydraulic roughness, durability, and corrosion and abrasion resistance. The three most common culvert materials are concrete (reinforced and nonreinforced), corrugated aluminum, and corrugated steel. Culverts may also be lined with other materials to inhibit corrosion and abrasion, or to reduce hydraulic resistance. For example, cor- rugated metal culverts may be lined with asphaltic concrete. A concrete box cul- vert and a corrugated metal arch culvert are depicted in figures I-S and 1-6 res- pecti vel y. 3. Inlets. A multitude of different inlet configurations are utilized on culvert barrels. These include both prefabricated and constructed-in-place installations. Commonly used inlet con- figurations include projecting culvert barrels, cast-in-place concrete head walls, precast or prefabricated end sections, and culvert ends mitered to conform to the fill slope. (figure 1-7) Structural stability, aesthetics, erosion control, and fill retention are considerations in the selection of various inlet configura- tions. . J . l ~ 1 ~ 2