Hydraulic Efficiency of Grate and Curb Inlets - Urban Drainage and ...

Solid Plexiglas ® was milled to produce the Type 13 grate shown in Figure 3-6. Copper
pipe and brass bar stock were used to fabricate the Type 16 grate shown in Figure 3-7. Curved
vanes on the Type 16 grate were constructed of copper pipe. Transitions from the gutter cross
slope to the inlet cross slope were built into the gutter panels. As a result of the need for variable
opening lengths in each inlet type, the gutter panels were built as modular elements which could
be removed and relocated within the gutter panel framework. Modeling clay was used to
smooth-out any irregularities in the curb, gutter, and inlet surfaces.
Figure 3-6: Type 13 grate photograph
Figure 3-7: Type 16 grate during fabrication
Type 13 and 16 inlets were used in a combination-inlet configuration, in which there was
a curb opening in addition to the grate. The Type R inlet is only a curb opening, which differed
from the curb opening used in the combination-inlet configuration. The model incorporated
depressed gutters in which the invert of the curb inlet was lower than the bottom of the gutter
flow line. With reference to Figure 2-3 presented previously, the curb inlet portion of the
combination inlet is most similar to the vertical throat type, whereas the Type R curb inlet is
most similar to the inclined throat type. There were several other configurations in which the
flow area of the inlet was reduced in some way: the curb portion of a combination inlet was
reduced to a “4-in.” height, the curb portion of a combination inlet was blocked-off completely,
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