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144 lines
3.9 KiB
Python
144 lines
3.9 KiB
Python
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"""
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Rainfall Intensity
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==================
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This module contains functions to calculate the intensity of
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a rainfall event for a given duration and return period.
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This function uses the Sherman intensity-duration-frequency curve.
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References
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----------
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- Aparicio, F. (1997): Fundamentos de Hidrología de Superficie.
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Balderas, México, Limusa. 303 p.
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- https://en.wikipedia.org/wiki/Intensity-duration-frequency_curve
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"""
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def rainfall_intensity(
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coefficient_k: float,
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coefficient_a: float,
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coefficient_b: float,
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coefficient_c: float,
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return_period: float,
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duration: float,
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) -> float:
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"""
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Calculate the intensity of a rainfall event for a given duration and return period.
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It's based on the Sherman intensity-duration-frequency curve:
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I = k * T^a / (D + b)^c
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where:
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I = Intensity of the rainfall event [mm/h]
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k, a, b, c = Coefficients obtained through statistical distribution adjust
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T = Return period in years
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D = Rainfall event duration in minutes
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Parameters
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----------
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coefficient_k : float
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Coefficient obtained through statistical distribution adjust.
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coefficient_a : float
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Coefficient obtained through statistical distribution adjust.
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coefficient_b : float
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Coefficient obtained through statistical distribution adjust.
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coefficient_c : float
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Coefficient obtained through statistical distribution adjust.
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return_period : float
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Return period in years.
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duration : float
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Rainfall event duration in minutes.
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Returns
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-------
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intensity : float
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Intensity of the rainfall event in mm/h.
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Raises
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------
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ValueError
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If any of the parameters are not positive.
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Examples
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--------
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>>> rainfall_intensity(1000, 0.2, 11.6, 0.81, 10, 60)
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49.83339231138578
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>>> rainfall_intensity(1000, 0.2, 11.6, 0.81, 10, 30)
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77.36319588106228
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>>> rainfall_intensity(1000, 0.2, 11.6, 0.81, 5, 60)
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43.382487747633625
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>>> rainfall_intensity(0, 0.2, 11.6, 0.81, 10, 60)
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Traceback (most recent call last):
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...
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ValueError: All parameters must be positive.
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>>> rainfall_intensity(1000, -0.2, 11.6, 0.81, 10, 60)
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Traceback (most recent call last):
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...
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ValueError: All parameters must be positive.
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>>> rainfall_intensity(1000, 0.2, -11.6, 0.81, 10, 60)
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Traceback (most recent call last):
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...
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ValueError: All parameters must be positive.
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>>> rainfall_intensity(1000, 0.2, 11.6, -0.81, 10, 60)
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Traceback (most recent call last):
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...
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ValueError: All parameters must be positive.
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>>> rainfall_intensity(1000, 0, 11.6, 0.81, 10, 60)
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Traceback (most recent call last):
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...
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ValueError: All parameters must be positive.
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>>> rainfall_intensity(1000, 0.2, 0, 0.81, 10, 60)
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Traceback (most recent call last):
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...
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ValueError: All parameters must be positive.
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>>> rainfall_intensity(1000, 0.2, 11.6, 0, 10, 60)
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Traceback (most recent call last):
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...
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ValueError: All parameters must be positive.
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>>> rainfall_intensity(0, 0.2, 11.6, 0.81, 10, 60)
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Traceback (most recent call last):
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...
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ValueError: All parameters must be positive.
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>>> rainfall_intensity(1000, 0.2, 11.6, 0.81, 0, 60)
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Traceback (most recent call last):
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...
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ValueError: All parameters must be positive.
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>>> rainfall_intensity(1000, 0.2, 11.6, 0.81, 10, 0)
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Traceback (most recent call last):
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...
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ValueError: All parameters must be positive.
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"""
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if (
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coefficient_k <= 0
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or coefficient_a <= 0
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or coefficient_b <= 0
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or coefficient_c <= 0
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or return_period <= 0
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or duration <= 0
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):
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raise ValueError("All parameters must be positive.")
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intensity = (coefficient_k * (return_period**coefficient_a)) / (
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(duration + coefficient_b) ** coefficient_c
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)
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return intensity
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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