The Rational Formula delivers an estimate of the peak flow Q [L3/T] for a catchment with area A [L2], depending on a forcing given by rainfall intensity i [L/T] and the runoff coefficient C [-]. The rational formula can be considered the first rainfall-runoff model proposed.

How do you calculate peak flow?

How to measure peak flow

Move the marker to the bottom of the numbered scale.

Stand up straight.

Take a deep breath.

Hold your breath while you place the mouthpiece in your mouth, between your teeth.

Blow out as hard and fast as you can in a single blow.

Write down the number you get.

What is peak flow in hydrology?

The maximum rate of discharge during the period of runoff caused by a storm is called a “peak flow”. The information about peak flows and associated volume of runoff during various floods that have been observed in the past can be complied by the analysis of the observed discharge data and runoff hydrographs.

What is rational formula?

The Rational Method is a set of formulae used to determine the peak discharge expected from a soil conservation structure design, such as a contour bank. The Empirical version is a simplification of the full Rational Method which uses parameter values that are based on experience or observation.

What are the factors which affect the peak flood flow?

Peak discharges within the rainstorm-flood area were found to be significantly related to seven factors: drainage-area size, rainfall intensity for a given duration and frequency, main-channel slope, basin length, surface area of lakes and ponds, the ratio of runoff to rainfall during the months of annual peak …

What is peak run off?

Peak discharge is determined by the area of the catchment above the structure and the rate of runoff expected from that catchment under the conditions for which the structure is designed. • Runoff is a sporadic occurrence. Most runoff is the result of occasional intense storm events.

Where is rational method used?

It has been used for over 150 years, and known as the Rational Method for nearly 100 years. It is widely used in the design of stormwater drainage systems, farm dam spillways, and small culverts in road and railway embankments.

How do you calculate peak flow rate?

The calculator allows input in either cm or inches, however, inches are transformed in cm that are used in the formula. Peak expiratory flow rate ( PEFR ) is estimated via one of these equations: Children PEFR = ((Height in cm – 100) x 5) + 100. Adult Men = (((Height in m x 5.48) + 1.58) – (Age x 0.041)) x 60.

What is the unit of measurement for peak flow?

Specifically, the unit of the peak flow meter scale is liters per minute. Each reading is compared with the initial or baseline reading, which is taken when you are breathing without any symptoms. Normal readings of peak flow meters depend on a person’s age, sex, and height.

What is normal peak flow measurement?

A normal peak flow will vary according to height, age and gender. Adults should achieve readings of 400 to 700 litres per minute, with men generally higher. Readings tend to be lower in the morning and will be affected by how recently the person has taken his or her inhaler to expand the airways.

What is the average peak flow rate?

Three zones of measurement are commonly used to interpret peak flow rates. It is easy to relate the three zones to the traffic light colors: green, yellow and red. In general, a normal peak flow rate can vary as much as 20 percent.