Topic II. 5. Rain Measurement: Parameters, Pluviographs, Hyetographs and Hydrographs. Selection of Design Rain

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Topic II. 5. Rain Measurement Parameters,Pluviog
raphs, Hyetographs and Hydrographs.Selection of
Design Rain

• Rain Parameters
• Rain duration - t, min
• Rain depth - h, mm
• Rain intensity
• Physical intensity - i, mm/min
• Technical intensity - q, l/s.ha
• Rain frequency - m, year-1
• Return period - P, years

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Rain Parameters

• Rain Intensities Relationship
• Kinds of Rain Intensity
• Mean intensity
• Partial intensity
• Momentum intensity
• Return Period and Rain
• Frequency Relationship

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Rain Parameters

• Rain Frequency and
• Rain Probability
• Rain frequency - m, y-1
• q1, q2, q3,qiqn-1, qn
• q1 gt q2 gt q3 gt gt qi gt gt qn-1 gt qn
• where qi position in the row is N0 i
• Rain probability - p
• q1, q2, q3,qiqn-1, qn ? totally n number for
  the period of observation - T
• q1 gt q2 gt q3 gt gt qi gt gt qn-1 gt qn
• , when n ? ?

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Rain Parameters

• Rain Parameters Relationships
• Example
• Given T 20 years n 1000 No 4
• Then, ,y-1
• ,y

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Rainfall (Precipitation) Measurement

• Rain Gauges
• Standard rain gauge
• Pluviographs (recording rain gauges)
• Hellmann type
• Tipping bucket type
• Weighing type
• Radars

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Precipitation Measurement

• Rain-Gauges

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Precipitation Measurement

• Radar for Precipitation Measuring
• Radar beam parameters
• wave length - 3 - 10 cm
• wave frequency - 500 - 1000 Hz
• Reflecting beam power - Pr
• Formula of Marshal - Palmer

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Rainfall and Runoff ParametersDependence on Time

• Pluviograph
• (Rain-gauge record)
• ?h f(t)
• Hyetograph
• q f(t)
• Hydrograph
• Q f(t)

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Rain Duration - Intensity - Frequency (DIF)
Relationships

• I. Formulas Implicit in Respect
• to the Return Period
• Formula of Talbot (1891)
• Formula of Belov (1922)-Montana

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Rain Duration - Intensity - Frequency (DIF)
Relationships

• II. Formulas Explicit in Respect
• to the Return Period
• Formula of Belov (1932)
• Formulas of Dimovski (1987)

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Rain-Gauge Records Reading

• Pluviographs shapes
• Pluviographs shapes impact
• on the relevant hydrographs
• Storms pluviographs shape
• Rain-gauge records reading
• Method of maximum intensity

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Return Period Impacton the Design Rain Selection

• Factors Influencing the
• Return Period Selection
• Kind of the sewer system
• Level of the settlement development
• Terrain topography
• Streets width
• Underground infrastructure density

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Selection of Design Rain

• Based on historical rain-gauge records
  (graphically)
• Based on prescribed return period values
• Separate sewer system - P 1 - 5 years
• Combined sewer system - P 1 - 10 years, as
  follows
• Settlements of I and II functional type - P 3 -
  10 years
• Settlements of III and IV functional type - P 2
  - 5 years
• Settlements of V, VI and VII functional type - P
  1 - 2 years