# Flow through Culverts - PowerPoint PPT Presentation

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Flow through Culverts. Flow through Culverts. A short passage way for flow under a highway, railroad or other embankment is referred to as a culvert. Culvert shape may be circular, rectangular, arch or elliptical.

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Flow through Culverts

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## Flow through Culverts

### Flow through Culverts

• A short passage way for flow under a highway, railroad or other embankment is referred to as a culvert.

• Culvert shape may be circular, rectangular, arch or elliptical.

• Several flow conditions are possible and these conditions depend upon several parameters.

• Flow control (upstream or downstream)

• Depending upon the head and the tailwater levels, the control may shift from the inlet to the outlet and vice versa as these water levels change.

### Flow Capacity

• A curve relating the headwater level to the rate of discharge through the culvert is referred to as the rating curve or the performance curve.

• For flow capacity determination, pick rating curve that gives lower discharge among inlet and outlet rating curves

### Inlet Control

• A culvert does not flow full even if the entrance is submerged if the Head at inlet is less than , where is the height of the culvert at the entrance and = the upstream water level – the culvert invert level

(Chaudhry, 2008)

### Rate of Discharge [Henderson, 1966]

• Unsubmerged entrance

= Culvert width, coefficient accounts for contraction on the sides. For square edge sides, ; and for slightly rounded sides .

• Submerged entrance

accounts for contraction at the sides and the top. For square edge entrance, ; and for rounded edges .

### Outlet Control

• In the outlet control, the culvert either flows full or partially full.

is total losses

is elevation of the water level

(Chaudhry, 2008)

### Flow Measurement

• Employing the critical flow characteristics, only flow depth is sufficient to estimate rate of discharge.

• Flumes: discharge measurement is based on the assumption that critical flow is produced by constricting the width, raising the bottom, or combination of the two. Then the measurement of a single flow depth is sufficient to determine the discharge.

• Parshall flume is a commonly used flume (standing wave flumes)

(Chaudhry, 2008)