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Stormwater Overland Flow
TP108 CALCULATIONS
Site: 52 North Road, Clevedon
Project No. 1169
Prepared by : B Xiao
Checked :V Crang
Date: 19 August 2017
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2017
Location: catchment A Checked V Crang Date 21/08/2017
Job No 1169
Circle one: Present Developed (Pervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
C urban lawn 74 0.36 27
* from Appendix B on TP 108 Totals = 0.36 27
Pervious area 30% of Catchment
CN (weighted) = total product / total area = 74.0
Ia (weighted) = 5 x pervious area / total area = 5.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.16 km (along drainage path)
Catchment slope ……… Sc = 0.025 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 74.0 / (200-74.0) = 0.59
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.20.66
x 0.59-0.55
x 0.023-0.30
= 0.102 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.07 hrs
Project: 52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao
Location: Catchment A Checked V Crang
Job No 1169
Circle one: Present Developed (impervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
Building, Roads etc 98 0.83 81
* from Appendix B Totals = 0.83 81
impervious area 65%
CN (weighted) = total product / total area = 98.0
Ia (weighted) = 5 x pervious area / total area = 0.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.16 km (along drainage path)
Catchment slope ……… Sc = 0.025 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 98.0 / (200-98.0) = 0.96
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.200.66
x 0.96-0.55
x 0.023-0.30
= 0.077 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.05 hrs
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B XIAO Date 21/08/2017
Location: Catchment A V CRANG
Job No 1169
Circle one: Present Developed (Pervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0036 km2
Runoff Curve No CN = 74.0
Initial abstraction Ia = 5.00 mm
Time of concentration tc = 0.102 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 89.2 mm
Storm #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm
plus
16.8%
climate
change 217
5. Compute C*= P24 - 2Ia 0.54
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.132
(from fig 5.1)
7. Peak Flow rate, qp(A) = q* A P24 (m
3 / s) 0.103
8. Runoff depth,Q24 = (P24 - Ia)2
mm 149.20
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 537
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: Catchment A Checked V Crang
Job No 1169
Circle one: Present Developed (impervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0083 km2
Runoff Curve No CN = 98.0
Initial abstraction Ia = 0.00 mm
Time of concentration tc = 0.077 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 5.18 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm
plus
16.8%
climate
change 217
5. Compute C*= P24 - 2Ia 0.95
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.177
(from fig 5.1)
7. Peak Flow rate, qp(A) = q* A P24 (m
3 / s) 0.319
8. Runoff depth,Q24 = (P24 - Ia)2
mm 211.94
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 1759
Project: 52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2017
Location: catchment B Checked V Crang
Job No 1169
Circle one: Present Developed (Pervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
C urban lawn 74 0.14 10
* from Appendix B on TP 108 Totals = 0.14 10
Pervious area 30% of Catchment
CN (weighted) = total product / total area = 74.0
Ia (weighted) = 5 x pervious area / total area = 5.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.07 km (along drainage path)
Catchment slope ……… Sc = 0.006 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 74.0 / (200-74.0) = 0.59
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.150.66
x 0.59-0.55
x 0.045-0.30
= 0.090 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.06 hrs
Project: 52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2017
Location: Catchment B Checked V Crang
Job No 1169
Circle one: Present Developed (impervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
Building, Roads etc 98 0.32 31
* from Appendix B Totals = 0.32 31
impervious area 65%
CN (weighted) = total product / total area = 98.0
Ia (weighted) = 5 x pervious area / total area = 0.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.07 km (along drainage path)
Catchment slope ……… Sc = 0.006 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 98.0 / (200-98.0) = 0.96
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.150.66
x 0.96-0.55
x 0.045-0.30
= 0.069 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.05 hrs
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: Catchment B Checked V Crang
Job No 1169
Circle one: Present Developed (Pervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0014 km2
Runoff Curve No CN = 74.0
Initial abstraction Ia = 5.00 mm
Time of concentration tc = 0.090 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 89.2 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm
plus
16.8%
climate
change 217
5. Compute C*= P24 - 2Ia 0.54
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.145
(from fig 5.1)
7. Peak Flow rate, qp(B) = q* A P24 (m
3 / s) 0.044
8. Runoff depth,Q24 = (P24 - Ia)2
mm 149.20
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 209
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: Catchment B Checked V Crang
Job No 1169
Circle one: Present Developed (impervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0032 km2
Runoff Curve No CN = 98.0
Initial abstraction Ia = 0.00 mm
Time of concentration tc = 0.069 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 5.18 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm
plus
16.8%
climate
change 217
5. Compute C*= P24 - 2Ia 0.95
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.177
(from fig 5.1)
7. Peak Flow rate, qp(B) = q* A P24 (m
3 / s) 0.123
8. Runoff depth,Q24 = (P24 - Ia)2
mm 211.94
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 678
Project: 52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2014
Location: catchment C Checked V Crang
Job No 1169
Circle one: Present Developed (Pervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
C urban lawn 74 0.07 5
* from Appendix B on TP 108 Totals = 0.07 5
Pervious area 30% of Catchment
CN (weighted) = total product / total area = 74.0
Ia (weighted) = 5 x pervious area / total area = 5.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.07 km (along drainage path)
Catchment slope ……… Sc = 0.051 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 74.0 / (200-74.0) = 0.59
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.150.66
x 0.59-0.55
x 0.023-0.30
= 0.048 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.03 hrs
Project:52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2017
Location: Catchment C Checked V Crang
Job No 1169
Circle one: Present Developed (impervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
Building, Roads etc 98 0.16 16
* from Appendix B Totals = 0.16 16
impervious area 65%
CN (weighted) = total product / total area = 98.0
Ia (weighted) = 5 x pervious area / total area = 0.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.07 km (along drainage path)
Catchment slope ……… Sc = 0.051 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 98.0 / (200-98.0) = 0.96
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.150.66
x 0.96-0.55
x 0.023-0.30
= 0.036 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.02 hrs
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: Catchment C Checked V Crang
Job No 1169
Circle one: Present Developed (Pervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0007 km2
Runoff Curve No CN = 74.0
Initial abstraction Ia = 5.00 mm
Time of concentration tc = 0.090 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 89.2 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm plus
16.8% climate
change 217
5. Compute C*= P24 - 2Ia 0.54
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.145
(from fig 5.1)
7. Peak Flow rate, qp(C) = q* A P24 (m
3 / s) 0.022
8. Runoff depth,Q24 = (P24 - Ia)2
mm 149.20
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 104
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: Catchment C Checked V Crang
Job No 1169
Circle one: Present Developed (impervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0016 km2
Runoff Curve No CN = 98.0
Initial abstraction Ia = 0.00 mm
Time of concentration tc = 0.069 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 5.18 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm
plus16.8%
climate change 217
5. Compute C*= P24 - 2Ia 0.95
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.177
(from fig 5.1)
7. Peak Flow rate, qp(C) = q* A P24 (m
3 / s) 0.061
8. Runoff depth,Q24 = (P24 - Ia)2
mm 211.94
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 339
Project: 52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2017
Location: catchment D Checked V Crang
Job No 1169
Circle one: Present Developed (Pervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
C urban lawn 74 0.10 7
* from Appendix B on TP 108 Totals = 0.10 7
Pervious area 30% of Catchment
CN (weighted) = total product / total area = 74.0
Ia (weighted) = 5 x pervious area / total area = 5.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.12 km (along drainage path)
Catchment slope ……… Sc = 0.007 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 74.0 / (200-74.0) = 0.59
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.110.66
x 0.59-0.55
x 0.0270.30
= 0.123 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.08 hrs
Project: 52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2017
Location: Catchment D Checked V Crang
Job No 1169
Circle one: Present Developed (impervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
Building, Roads etc 98 0.24 24
* from Appendix B Totals = 0.24 24
impervious area 65%
CN (weighted) = total product / total area = 98.0
Ia (weighted) = 5 x pervious area / total area = 0.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.12 km (along drainage path)
Catchment slope ……… Sc = 0.007 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 98.0 / (200-98.0) = 0.96
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.110.66
x 0.96-0.55
x 0.027-0.30
= 0.094 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.06 hrs
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: Catchment D Checked V Crang
Job No 1169
Circle one: Present Developed (Pervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0010 km2
Runoff Curve No CN = 74.0
Initial abstraction Ia = 5.00 mm
Time of concentration tc = 0.123 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 89.2 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm
plus 16.8%
climate
change 217
5. Compute C*= P24 - 2Ia 0.54
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.145
(from fig 5.1)
7. Peak Flow rate, qp(D) = q* A P24 (m
3 / s) 0.031
8. Runoff depth,Q24 = (P24 - Ia)2
mm 149.20
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 149
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: catchment D Checked V Crang
Job No 1169
Circle one: Present Developed (impervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0024 km2
Runoff Curve No CN = 98.0
Initial abstraction Ia = 0.00 mm
Time of concentration tc = 0.094 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 5.18 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm
plus 16.8%
climate
change 217
5. Compute C*= P24 - 2Ia 0.95
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.177
(from fig 5.1)
7. Peak Flow rate, qp(D) = q* A P24 (m
3 / s) 0.092
8. Runoff depth,Q24 = (P24 - Ia)2
mm 211.94
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 509
Project: 52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2017
Location: catchment E Checked V Crang
Job No 1169
Circle one: Present Developed (Pervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
C urban lawn 74 0.12 9
* from Appendix B on TP 108 Totals = 0.12 9
Pervious area 30% of Catchment
CN (weighted) = total product / total area = 74.0
Ia (weighted) = 5 x pervious area / total area = 5.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.10 km (along drainage path)
Catchment slope ……… Sc = 0.007 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 74.0 / (200-74.0) = 0.59
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.110.66
x 0.59-0.55
x 0.0270.30
= 0.109 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.07 hrs
Project: 52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2017
Location: Catchment E Checked V Crang
Job No 1169
Circle one: Present Developed (impervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
Building, Roads etc 98 0.29 28
* from Appendix B Totals = 0.29 28
impervious area 65%
CN (weighted) = total product / total area = 98.0
Ia (weighted) = 5 x pervious area / total area = 0.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.10 km (along drainage path)
Catchment slope ……… Sc = 0.007 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 98.0 / (200-98.0) = 0.96
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.110.66
x 0.96-0.55
x 0.027-0.30
= 0.083 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.06 hrs
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: Catchment E Checked V Crang
Job No 1158
Circle one: Present Developed (Pervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0012 km2
Runoff Curve No CN = 74.0
Initial abstraction Ia = 5.00 mm
Time of concentration tc = 0.123 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 89.2 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm
plus 16.8%
climate
change 217
5. Compute C*= P24 - 2Ia 0.54
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.145
(from fig 5.1)
7. Peak Flow rate, qp(E) = q* A P24 (m
3 / s) 0.038
8. Runoff depth,Q24 = (P24 - Ia)2
mm 149.20
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 179
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: Catchment E Checked V Crang
Job No 1169
Circle one: Present Developed (impervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0029 km2
Runoff Curve No CN = 98.0
Initial abstraction Ia = 0.00 mm
Time of concentration tc = 0.094 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 5.18 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm
plus 16.8%
climate
change 217
5. Compute C*= P24 - 2Ia 0.95
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.177
(from fig 5.1)
7. Peak Flow rate, qp(E) = q* A P24 (m
3 / s) 0.111
8. Runoff depth,Q24 = (P24 - Ia)2
mm 211.94
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 615
Project: 52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2017
Location: catchment F Checked V Crang
Job No 1169
Circle one: Present Developed (Pervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
C urban lawn 74 0.23 17
* from Appendix B on TP 108 Totals = 0.23 17
Pervious area 30% of Catchment
CN (weighted) = total product / total area = 74.0
Ia (weighted) = 5 x pervious area / total area = 5.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.14 km (along drainage path)
Catchment slope ……… Sc = 0.080 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 74.0 / (200-74.0) = 0.59
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.110.66
x 0.59-0.55
x 0.0270.30
= 0.066 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.04 hrs
Project: 52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2017
Location: Catchment F Checked V Crang
Job No 1158
Circle one: Present Developed (impervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
Building, Roads etc 98 0.54 53
* from Appendix B Totals = 0.54 53
impervious area 65%
CN (weighted) = total product / total area = 98.0
Ia (weighted) = 5 x pervious area / total area = 0.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.14 km (along drainage path)
Catchment slope ……… Sc = 0.080 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 98.0 / (200-98.0) = 0.96
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.110.66
x 0.96-0.55
x 0.027-0.30
= 0.050 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.03 hrs
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: Catchment F Checked V Crang
Job No 1158
Circle one: Present Developed (Pervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0023 km2
Runoff Curve No CN = 74.0
Initial abstraction Ia = 5.00 mm
Time of concentration tc = 0.123 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 89.2 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm
plus 16.8%
climate
change 217
5. Compute C*= P24 - 2Ia 0.54
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.145
(from fig 5.1)
7. Peak Flow rate, qp(F) = q* A P24 (m
3 / s) 0.072
8. Runoff depth,Q24 = (P24 - Ia)2
mm 149.20
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 343
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: Catchment F Checked V Crang
Job No 1169
Circle one: Present Developed (impervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0054 km2
Runoff Curve No CN = 98.0
Initial abstraction Ia = 0.00 mm
Time of concentration tc = 0.094 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 5.18 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm
plus 16.8%
climate
change 217
5. Compute C*= P24 - 2Ia 0.95
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.177
(from fig 5.1)
7. Peak Flow rate, qp(F) = q* A P24 (m
3 / s) 0.207
8. Runoff depth,Q24 = (P24 - Ia)2
mm 211.94
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 1144
Project: 52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2017
Location: catchment G Checked V Crang
Job No 1169
Circle one: Present Developed (Pervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
C urban lawn 74 0.13 10
* from Appendix B on TP 108 Totals = 0.13 10
Pervious area 30% of Catchment
CN (weighted) = total product / total area = 74.0
Ia (weighted) = 5 x pervious area / total area = 5.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.14 km (along drainage path)
Catchment slope ……… Sc = 0.080 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 74.0 / (200-74.0) = 0.59
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.110.66
x 0.59-0.55
x 0.0270.30
= 0.066 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.04 hrs
Project: 52 North Road, Clevedon
Worksheet 1: Runoff Parameters
and Time of Concentration
By B Xiao Date 21/08/2017
Location: Catchment G Checked V Crang
Job No 1158
Circle one: Present Developed (impervious)
1. Runoff Curve Number (CN) and Initial Abstraction (Ia)
Soil name Cover description Curve Area Product
and (cover type, treatment & Number (ha) of CN x
classification hydrologic condition) CN* area
Building, Roads etc 98 0.30 29
* from Appendix B Totals = 0.30 29
impervious area 65%
CN (weighted) = total product / total area = 98.0
Ia (weighted) = 5 x pervious area / total area = 0.00 mm
2. Time of Concerntration
Channelisation factor ……… C = 0.60 (from Table 4.2)
Catchment length ……… L = 0.14 km (along drainage path)
Catchment slope ……… Sc = 0.080 m/m (by equal area method)
Runoff factor, CN / (200 - CN) = 98.0 / (200-98.0) = 0.96
tc = 0.14 C L0.66
(CN / (200 - CN))-0.55
Sc-0.30
= 0.14 x 0.6 x 0.110.66
x 0.96-0.55
x 0.027-0.30
= 0.050 hrs
SCS Lag for HEC-HMS ………. Tp = 2 / 3 tc = 0.03 hrs
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: Catchment G Checked V Crang
Job No 1158
Circle one: Present Developed (Pervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0013 km2
Runoff Curve No CN = 74.0
Initial abstraction Ia = 5.00 mm
Time of concentration tc = 0.123 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 89.2 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm plus
16.8% climate
change 217
5. Compute C*= P24 - 2Ia 0.54
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.145
(from fig 5.1)
7. Peak Flow rate, qp(F) = q* A P24 (m
3 / s) 0.041
8. Runoff depth,Q24 = (P24 - Ia)2
mm 149.20
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 194
Project: 52 North Road, Clevedon
Worksheet 2: Graphical Peak Flow rate
By B Xiao Date 21/08/2017
Location: Catchment G Checked V Crang
Job No 1169
Circle one: Present Developed (impervious)
1. Data (from Worksheet 1)
Catchment area A = 0.0030 km2
Runoff Curve No CN = 98.0
Initial abstraction Ia = 0.00 mm
Time of concentration tc = 0.094 hrs
2.Calculate Storage, S = (1000 / CN - 10) x 25.4 = 5.18 mm
Storm# #1
3. Average recurrence Interval, ARI (yr) 100 Year
4. 24 hour rainfalll depth, P24 (mm)
185mm plus
16.8% climate
change 217
5. Compute C*= P24 - 2Ia 0.95
P24 - 2Ia + 2S
6. Specific peak flow rate q* 0.177
(from fig 5.1)
7. Peak Flow rate, qp(F) = q* A P24 (m
3 / s) 0.115
8. Runoff depth,Q24 = (P24 - Ia)2
mm 211.94
(P24 - Ia) + S
9. Runoff volume, V24 = 1000 x Q24 A (m3) 636
Project: 52 North Road, Clevedon
OVERLAND FLOWPATH CALCULATION
SECTION A-A
PROJECT : 52 North Road, Clevedon
Job No. : 1169 Calculation by : B Xiao
Date : August 2017 Checked by: V Crang
Qd (100) 1 in 100 year storm, use TP108
Qd(100) = Qd(100)pervious+Qd(100)impervious
Qd (100)pervious = 0.103 m³/s
Qd (100)impervious = 0.319 m³/s
Qd (100) = 0.422 m³/s
Qc = A*R^(2/3)*S^(1/2)/n
n = 0.013 concrete
S = 1.90% longitudinal grade
H= 0.11 m
W = 6.0 m
P = 6.27
R = A/P
A = 0.31 m2
R = 0.049 m
Qc (capacity)= 0.444 m3/s > Qd (net) = 0.422 m³/s OK
OVERLAND FLOWPATH CALCULATION
SECTION B-B
PROJECT : 52 North Road, Clevedon
Job No. : 1169 Calculation by : B Xiao
Date : August 2017 Checked by: V Crang
Qd (100) 1 in 100 year storm, use TP108
Qd(100) = Qd(100)pervious+Qd(100)impervious
Qd (100)pervious = 0.147 m³/s from TP108 calcls(CATCHMENT A+B)
Qd (100)impervious = 0.442 m³/s from TP108 calcls(CATCHMENT A+B)
Qd (100) = 0.589 m³/s
Qc = A*R^(2/3)*S^(1/2)/n
n = 0.020 concrete+berm grass
S = 0.60% longitudinal grade
H= 0.19 m
W = 10.14 m
P = 10.41
R = A/P
A = 0.84 m2
R = 0.081 m
Qc (capacity)= 0.609 m3/s > Qd (net) = 0.59 m³/s OK
OVERLAND FLOWPATH CALCULATION
SECTION C-C
PROJECT : 52 North Road, Clevedon
Job No. : 1169 Calculation by : B Xiao
Date : August 2017 Checked by: V Crang
Qd (100) 1 in 100 year storm, use TP108
Qd(100) = Qd(100)pervious+Qd(100)impervious
Qd (100)pervious = 0.169 m³/s from TP108 calcls(CATCHMENT A+B+C)
Qd (100)impervious = 0.503 m³/s from TP108 calcls(CATCHMENT A+B+C)
Qd (100) = 0.672 m³/s
Qc = A*R^(2/3)*S^(1/2)/n
n = 0.020 concrete+grass
S = 5.10% longitudinal grade
H= 0.17 m
W = 6.3 m
P = 6.43
R = A/P
A = 0.39 m2
R = 0.060 m
Qc (capacity)= 0.672 m3/s > Qd (net) = 0.67 m³/s OK
OVERLAND FLOWPATH CALCULATION
SECTION D-D
PROJECT : 52 North Road, Clevedon
Job No. : 1169 Calculation by : B Xiao
Date : August 2017 Checked by: V Crang
Qd (100) 1 in 100 year storm, use TP108
Qd(100) = Qd(100)pervious+Qd(100)impervious
Qd (100)pervious = 0.116 m³/s from TP108 calcls CATCHMENT D+1/2 (A+B+C)
Qd (100)impervious = 0.344 m³/s from TP108 calcls CATCHMENT D+1/2 (A+B+C)
Qd (100) = 0.460 m³/s
Qc = A*R^(2/3)*S^(1/2)/n
n = 0.020 concrete+grass
S = 0.70% longitudinal grade
H= 0.21 m
W = 8.53 m
P = 8.66
R = A/P
A = 0.63 m2
R = 0.073 m
Qc (capacity)= 0.464 m3/s > Qd (net) = 0.46 m³/s OK
OVERLAND FLOWPATH CALCULATION
SECTION E-E
PROJECT : 52 North Road, Clevedon
Job No. : 1169 Calculation by : B Xiao
Date : August 2017 Checked by: V Crang
Qd (100) 1 in 100 year storm, use TP108
Qd(100) = Qd(100)pervious+Qd(100)impervious
Qd (100)pervious = 0.154 m³/s from TP108 calcls CATCHMENT D+E+1/2 (A+B+C)
Qd (100)impervious = 0.455 m³/s from TP108 calcls CATCHMENT D+E+1/2 (A+B+C)
Qd (100) = 0.609 m³/s
Qc = A*R^(2/3)*S^(1/2)/n
n = 0.020 concrete+grass
S = 0.70% longitudinal grade
H= 0.15 m
W = 15.00 m
P = 15.10
R = A/P
A = 0.94 m2
R = 0.062 m
Qc (capacity)= 0.619 m3/s > Qd (net) = 0.61 m³/s OK
OVERLAND FLOWPATH CALCULATION
SECTION F-F
PROJECT : 52 North Road, Clevedon
Job No. : 1169 Calculation by : B Xiao
Date : August 2017 Checked by: V Crang
Qd (100) 1 in 100 year storm, use TP108
Qd(100) = Qd(100)pervious+Qd(100)impervious
Qd (100)pervious = 0.072 m³/s from TP108 calcls
Qd (100)impervious = 0.207 m³/s from TP108 calcls
Qd (100) = 0.279 m³/s
Qc = A*R^(2/3)*S^(1/2)/n
n = 0.020 concrete+ grass
S = 5.80% longitudinal grade
H= 0.09 m
W = 3.86 m
P = 3.86
R = A/P
A = 0.18 m2
R = 0.047 m
Qc (capacity)= 0.284 m3/s > Qd (net) = 0.28 m³/s OK
OVERLAND FLOWPATH CALCULATION
SECTION G-G
PROJECT : 52 North Road, Clevedon
Job No. : 1169 Calculation by : B Xiao
Date : August 2017 Checked by: V Crang
Qd (100) 1 in 100 year storm, use TP108
Qd(100) = Qd(100)pervious+Qd(100)impervious
Qd (100)pervious = 0.126 m³/s from TP108 calcls CATCHMENT G+1/2 (A+B+C)
Qd (100)impervious = 0.368 m³/s from TP108 calcls CATCHMENT G+1/2 (A+B+C)
Qd (100) = 0.494 m³/s
Qc = A*R^(2/3)*S^(1/2)/n
n = 0.020 concrete+grass
S = 2.80% longitudinal grade
H= 0.18 m
W = 5.08 m
P = 6.56
R = A/P
A = 0.39 m2
R = 0.059 m
Qc (capacity)= 0.498 m3/s > Qd (net) = 0.49 m³/s OK
OVERLAND FLOWPATH CALCULATION
SECTION H-H
PROJECT : 52 North Road, Clevedon
Job No. : 1169 Calculation by : B Xiao
Date : August 2017 Checked by: V Crang
Qd (100) 1 in 100 year storm, use TP108
Qd(100) = Qd(100)pervious+Qd(100)impervious
Qd (100)pervious = 0.241 m³/s from TP108 calcls CATCHMENT A+B+C+D+E
Qd (100)impervious = 0.710 m³/s from TP108 calcls CATCHMENT A+B+C+D+E
Qd (100) = 0.951 m³/s
Qc = A*R^(2/3)*S^(1/2)/n
n = 0.032 grass
S = 4.30% longitudinal grade
H= 0.18 m
W = 3.87 m
P = 3.91
R = A/P
A = 0.55 m2
R = 0.140 m
Qc (capacity)= 0.956 m3/s > Qd (net) = 0.95 m³/s OK
