Page 523 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

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13.10 Street Inlets 481

Curb Inlets

(a) At grade (b) Depressed (c) Deflecting
Gutter Inlets

(d ) At grade (e) Depressed
Combination curb Multiple curb
and gutter inlet and gutter inlet

(f ) Depressed (g) At grade
Figure 13.10 Types of Street Inlets.

is whether the inlet is located on grade or in sag, because the design criteria and the equa-
tions involved differ. Inlets on grade are located on a slope and intercept a portion of the
water as it flows past. Inlets in sag are located at a point where runoff from a given area
will ultimately collect, and these inlets are normally designed to capture 100% of the sur-
face flow; otherwise, flooding will occur in the surrounding area.
The intake capacity of inlets, particularly curb inlets, increases with decreasing street
grade and increasing crown slope. However, curb inlets with diagonal deflectors in the gut-
ter along the opening become more efficient as grades become steeper. Gutter inlets are
more efficient than curb inlets in capturing gutter flow, but clogging by debris is a problem.
Combination inlets are better still, especially if gratings are placed downstream from curb

Figure 13.11 Street Inlet.
(Source: Wikipedia, http://en.wikipedia.org/wiki/Image:Storm_Drain.JPG.)