What is the formula for drainage?

The runoff, Q, for the roof area in drainage Zone A is: (1.00 x 1.5 x 500) / 96.23 = 7.79 gallons per minute. The runoff for the grass portion of drainage Zone A is: (0.35 x 1.5 x 900) / 96.23 = 4.91 gpm.

What is bridge deck drainage?

BRIDGE DECK DRAINAGE. Basic Concepts. Bridge drainage covers the collection and removal of waters from a bridge deck. To accomplish this function, drains are placed adjacent to curbs for collection of water which is then either dumped directly on the ground or is conveyed to a suitable disposal point.

What is a scupper on a bridge?

A scupper is a small opening in the bridge deck, curb, or barrier through which water can flow from the bridge deck. This program will only be considering the opening in the bridge deck.

How is drainage density calculated?

Drainage Density is the total length of all the streams and Rivers in a Drainage basin divided by the total area of the drainage basin.

How do bridges drain water?

Highway bridge decks are usually designed with slopes and cross fall to ensure efficient runoff drainage. Typically, the runoff is directed to downspouts on the bridge deck that discharge the water directly from the deck to below. Spacing of standard deck drains to convey runoff.

How do you size the drainage systems?

The sizing of drainage piping systems is based on fixture unit values. The fixture unit value takes into consideration the average rate of discharge, duration of use for a single operation and the interval between each operation of a plumbing fixture.

How should drainage be planned?

A drainage plan should look at how rainwater flows in and out of a building. It should include where it flows into the ground, downpipes, or drains into storm sewers. It should also ensure that water can reach where it needs to go without flooding and cause backups in sewer pipes or septic tanks.

What is the use of scupper drain?

Scuppers are used to provide an outlet through parapet walls or gravel stops on flat and built-up roofs to allow drainage of excess water. They can be used in conjunction with gutters an down spouts to diverts the flow to the desired location.

How do you calculate drainage?

Another way to calculate the drainage is find a weighted “C” value for the whole area contributing to the low spot. To calculate the weighted average, you take the multiply the area of each part for the zone by its corresponding “C” value. You then add these factors together and divide that by the total area of the contributing parts.

What is the rational method of calculating storm water runoff?

The Rational Method equation is: Q = C x I x A where: Q = Storm Water Runoff (in cubic feet per second) C = Coefficient of Runoff I = Rainfall Intensity (in inches per hour) A = Area of Drainage Zone (in acres) The equation above can be modified to give you runoff in gallons per minute.

How do you calculate the length of a drain grate?

The inlet grate must be of adequate length in the longitudinal direction to intercept the flow approachingit without excessive splash over. An estimate of the required drain length is given by the followingequation. = V/2 (d+d b)1/2(4) = length of clear opening of grate in feet (1.375 ft for grate in drain type C, D-1, and D-2)

How big of a drainage area do I need to divide?

For drainage areas greater than 200 acres, other methods can be used, or the drainage area can be divided into zones less than 200 acres.