TROY

1
GEM 4409HydrologyFall 2005

• TROY
• UNIVERSITY

2
Regional Analysis of Runoff

• Typical Equation
• Qp cAm
• Qp Peak Flow
• A Area of Drainage Basin
• c, m Regression Parameters

3
Regional Analysis of Runoff

• Other Equations

-m
Qp cAnA Qp cA(a-b log A) used
primarily in the Southwest Qp cA/(abA)m dA
used typically in Europe
a, b, c, d, m, n are statistical parameters
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USGS Regression Equations for Alabama
5
Rural Basins

• Table 1.
• Flood-peak discharge regression equations and
  associated statistics for streams that drain
  rural areas in Alabama
• Q Peak Flow for return period T (2 to 500 yrs)
  cfs
• A contributing drainage area square miles
• do., Do. ditto

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Alabamas Four Hydrologic Regions
Rural Basins Region 1 Q2
227 A0.672 Q5 374 A0.669 Q10 482 A0.669
Q25 627 A0.668 Q50 739 A0.667 Q100
855 A0.667 Q200 974 A0.666 Q500 1,135
A0.666
1
2
3
4
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Alabamas Four Hydrologic Regions
Rural Basins Region 2 Q2
163A0.664 Q5 295A0.654 Q10 406A0.648
Q25 573A0.640 Q50 716A0.634 Q100
877A0.628 Q200 1,057A0.622 Q500
1,327A0.614

1
2
3
4
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Alabamas Four Hydrologic Regions
Rural Basins Region 3 Q2
347A0.573 Q5 517A0.607 Q10 638A0.626
Q25 796A0.648 Q50 914A0.663 Q100
1,032A0.677 Q200 1,148A0.689 Q500
1,302A0.704
1
2
3
4
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Alabamas Four Hydrologic Regions
Rural Basins Region 4 Q2
169A0.616 Q5 313A0.608 Q10 444A0.600
Q25 650A0.592 Q50 831A0.587 Q100
1,035A0.583 Q200 1,262A0.579 Q500
1,601A0.576
1
2
3
4
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Rural Regression Equations

• Hydrologic Applicable Range of Drainage Area
  Area Square Miles
• Lower Limit Upper Limit
• Region 1 0.44 1,027
• Region 2 0.13 831
• Region 3 0.44 1,097
• Region 4 1.44 1,344

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Region 1 Rural Equations

• Average standard error Equivalent of
  prediction, in percent years of record

35 34 35 37 39 41 43 46
3 4 5 7 7 8 9 9
Q2 Q5 Q10 Q25 Q50 Q100 Q200 Q500
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Region 2 Rural Equations

• Average standard error Equivalent of
  prediction, in percent years of record

40 36 35 35 36 37 39 43
3 4 6 9 10 11 12 12
Q2 Q5 Q10 Q25 Q50 Q100 Q200 Q500
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Region 3 Rural Equations

• Average standard error Equivalent of
  prediction, in percent years of record

37 35 34 33 33 33 34 35
3 5 7 10 12 15 17 18
Q2 Q5 Q10 Q25 Q50 Q100 Q200 Q500
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Region 4 Rural Equations

• Average standard error Equivalent of
  prediction, in percent years of record

38 33 33 35 38 42 46 52
3 6 9 12 13 13 13 13
Q2 Q5 Q10 Q25 Q50 Q100 Q200 Q500
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Urban Basins

• Table 2.
• Flood-peak discharge regression equations and
  associated statistics for streams that drain
  urban areas in Alabama
• Q Peak Flow for return period T (2 to 100 yrs)
  cfs
• A contributing drainage area square miles
• IA impervious area
• do., Do. ditto

16
Alabamas Four Hydrologic Regions
Urban Basins Q2 150A0.70IA0.36
Q5 210A0.70 IA0.39 Q10 266A0.69 IA0.39 Q25
337A0.69 IA0.39 Q50 396A0.69 IA0.38 Q100
444A0.69 IA0.39
1
2
3
4
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Urban Regression Equations

• Applicable Range of Drainage Area
• Square Miles
• Lower Limit Upper Limit
• 0.16 83.5

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Urban Regression Equations

• Applicable Range of Impervious Area
• Lower Limit Upper Limit
• 8.3 42.9

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Urban Regression Equations

• Average standard error of prediction

26 24 24 24 25 25
Q2 Q5 Q10 Q25 Q50 Q100