The Papadaskis-Kazen equation is a method used for estimating the time of concentration in hydrologic calculations. It's particularly useful for preliminary sizing of stormwater management systems and drainage design. The time of concentration is an important parameter in determining the peak flow rates for various design storms.

The Papadaskis-Kazen equation is given by:

\[ Tc = 0.0028 \times L^0.77 \times S^{-0.385} \times N^{-0.2} \]

Where:
- \( Tc \) is the time of concentration in minutes.
- \( L \) is the flow path length in feet (or meters).
- \( S \) is the slope of the flow path (dimensionless, but it's usually calculated as a ratio of vertical drop to horizontal distance).
- \( N \) is the Manning's roughness coefficient (also dimensionless).

Here's how you can use the Papadaskis-Kazen equation for preliminary sizing:

1. **Determine Flow Path Length \( L \)**:
Measure the length of the flow path that rainwater would travel from the farthest point to the outlet point.

2. **Calculate Slope \( S \)**:
Calculate the slope of the flow path, typically expressed as the ratio of vertical drop to horizontal distance.

3. **Select Manning's Roughness Coefficient \( N \)**:
The Manning's roughness coefficient depends on the surface and channel characteristics. For example, a grassy field might have a different \( N \) value compared to a paved street. Consult engineering references or guidelines to estimate the appropriate \( N \) value for your specific situation.

4. **Plug Values into the Equation**:
Plug the values of \( L \), \( S \), and \( N \) into the Papadaskis-Kazen equation to calculate the time of concentration (\( Tc \)). https://krowddarden.one

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Hello,
The Papadaskis-Kazen method is a commonly used hydrological method for estimating time of concentration, which is a key parameter in many stormwater design calculations, such as sizing of stormwater detention facilities and culverts.

To use the Papadaskis-Kazen method, you will need the following information:

Watershed area (in square miles or hectares)
Average slope of the watershed (as a percentage)
Length of the longest flow path in the watershed (in feet or meters)
Soil type and land use of the watershed
Once you have this information, you can use the following equation to calculate the time of concentration (Tc):

Tc = 0.0124 * (L^0.83) * (S^-0.5) * (A^0.4) * (CN/100)^-1.4

Where:

Tc is the time of concentration in minutes
L is the longest flow path in feet or meters
S is the average slope of the watershed as a decimal (e.g. 0.05 for a 5% slope)
A is the watershed area in acres or hectares
CN is the curve number, which is a dimensionless parameter that depends on the soil type and land use of the watershed. You can find CN values for different land uses and soil types in hydrology textbooks or online resources.
Note that this equation assumes that the watershed is homogeneous and that rainfall intensity is uniform throughout the watershed. It is also important to note that this equation is only an estimate and that actual time of concentration may vary depending on the complexity and shape of the watershed. Therefore, it is recommended to use this equation as a preliminary sizing tool and to verify the results with more detailed analyses.

TR-55 is intended to be used for midsize basins, greater than 2.5 km2, with time of concentration up to 10 hours. https://www.expresshr.onl/

Hello,
To calculate the Time of Concentration (Tc) using the Papadaskis-Kazen method for preliminary sizing in Arizona, you can use the following equation:

Tc = 0.25*(L/[(0.013S)^0.5])(1+(Ia/100))^0.75

Where:
Tc = Time of Concentration (minutes)
L = Length of the longest flow path (feet)
S = Average slope of the longest flow path (decimal)
Ia = Watershed impervious area (percentage)

Note that this equation assumes a watershed with moderate cover (less than 50% impervious area) and a flow path with uniform slope. https://www.nexus-iceland.com/

Also, be aware that this equation only provides an estimate of Tc and should be used for preliminary sizing only. For detailed design, you may need to use more sophisticated methods that take into account the specific characteristics of your watershed, such as the NRCS TR-55 method or HEC-HMS.

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