Attachment 18. Drainage Catchment Areas and Surface Type

April 20, 2021Pages 113–1142 sections

Visual and data sheet for drainage catchment areas and surface types.

Catchment area calculationsRunoff coefficients

Attachment 18 - Page 1 of 2

Drainage Catchment Area Map

This page contains a site plan map for the drainage catchment area of a development project, showing building blocks labeled A through Q, a pipe network with manholes (DMH), and color-coded catchment regions.

Catchment Areas

802 m² TO DMH 4
1890 m² TO DMH 4A
4547 m² TO DMH 5
1634 m² TO DMH 6
1597 m² TO DMH 7
1237 m² TO DMH 8
3785 m² TO DMH 9
2647 m² TO DMH 10
603 m² TO DMH 11
4149 m² TO DMH 12
3700 m² TO DMH 13

Surface Type

HARD SURFACE 702 m², LANDSCAPED 100 m²
HARD SURFACE 1206 m², LANDSCAPED 684 m²
HARD SURFACE 2378 m², LANDSCAPED 2169 m²
HARD SURFACE 942 m², LANDSCAPED 692 m²
HARD SURFACE 1196 m², LANDSCAPED 401 m²
HARD SURFACE 1172 m², LANDSCAPED 65 m²
HARD SURFACE 2081 m², LANDSCAPED 666 m², NATURAL VEGETATION 738 m², EXPOSED ROCK 300 m²
HARD SURFACE 861 m², LANDSCAPED 666 m², NATURAL VEGETATION 870 m², EXPOSED ROCK 250 m²
HARD SURFACE 603 m²
HARD SURFACE 2988 m², LANDSCAPED 490 m², NATURAL VEGETATION 671 m²
HARD SURFACE 2192 m², LANDSCAPED 1508 m²

Page 113–114

Attachment 18 - Page 2 of 2

Drainage System Design and Calculation Sheet

Project No.: 2019-2522 Project Description: West Park at Thetis - Storm Sewer Sizing Location: View Royal, BC

Design Parameters:

Design Return Period: 72% of 2 year / 100 year
Manning "n": 0.013 for conc. or PVC; 0.024 for CMP; 0.030 for ditches
Formula: $Q = CAiN$ where "N" = 0.00278 for Victoria - Gonzales
Intensity Formula: $i = \lambda a T^{B}$
$\lambda$: 0.72
For 2 yr (72%): "a" = 7.500, "B" = 0.419
For 100 yr: "a" = 16.900, "B" = 0.419

MH/ Node From	MH/ Node To	Area (ha) A	"C"	A*C	Σ(A*C)	Inlet (min)	Sect. (min)	Total (min)	Rain Int. "i" (mm/hr)	Q cms	Q l/s	S (%)	D (mm)	L (m)	V cap. (m/s)	Q cap. (cms)	Q/Qcap (%)
DMH12	DMH11	0.415	0.72	0.30	0.30	8.00	0.63	8.63	16.90 / 38.08	0.010 / 0.023	10.16 / 22.90	0.80	250	41.00	1.084	0.053	19% / 43%
DMH11	DMH10	0.060	0.95	0.06	0.36	8.63	0.48	9.11	16.52 / 37.23	0.012 / 0.027	11.83 / 26.66	0.80	250	31.00	1.084	0.053	22% / 50%
DMH10	DMH09	0.265	0.48	0.13	0.49	9.11	0.48	9.58	16.17 / 36.45	0.016 / 0.035	15.71 / 35.40	0.80	250	31.00	1.084	0.053	30% / 67%
DMH09	DMH08	0.379	0.65	0.25	0.73	9.58	0.51	10.10	15.82 / 35.66	0.023 / 0.052	23.19 / 52.25	0.80	300	37.71	1.224	0.086	27% / 60%
DMH08	DMH07	0.124	0.91	0.11	0.84	10.10	0.33	10.42	15.62 / 35.19	0.026 / 0.059	26.40 / 59.50	1.73	300	35.09	1.799	0.127	21% / 47%
DMH07	DMH06	0.160	0.76	0.12	0.97	10.42	0.14	10.56	15.53 / 34.99	0.030 / 0.068	30.04 / 67.68	5.82	300	28.00	3.300	0.233	13% / 29%
DMH06	DMH05	0.163	0.63	0.10	1.07	10.56	0.06	10.63	15.49 / 34.90	0.033 / 0.075	33.17 / 74.73	8.90	375	17.83	4.736	0.523	6% / 14%
DMH05	DMH04A	0.455	0.59	0.27	1.34	10.63	0.23	10.85	15.35 / 34.59	0.041 / 0.093	41.15 / 92.72	12.00	375	75.00	5.499	0.607	7% / 15%
DMH04A	DMH04	0.189	0.68	0.13	1.47	10.85	0.14	11.00	15.27 / 34.40	0.045 / 0.101	44.84 / 101.04	11.12	375	46.00	5.294	0.585	8% / 17%
DMH04	DMH3 (STC)	0.080	0.00	0.00	1.47	11.00	0.39	11.39	15.04 / 33.90	0.044 / 0.100	44.18 / 99.56	1.50	375	46.00	1.944	0.215	21% / 46%
DMH3 (STC)	DMH02	0.000	0.00	0.00	1.47	11.39	0.05	11.44	15.02 / 33.84	0.044 / 0.099	44.11 / 99.39	5.26	375	10.00	3.641	0.402	11% / 25%
DMH02	DMH01 (FC)	0.000	0.00	0.00	1.47	11.44	0.06	11.50	14.98 / 33.77	0.044 / 0.099	44.01 / 99.16	2.80	375	10.00	2.656	0.293	15% / 34%
DMH13	DMH04A	0.370	0.64	0.24	0.24	8.00	0.23	8.23	17.24 / 38.85	0.008 / 0.019	8.23 / 18.54	3.61	250	32.00	2.302	0.113	7% / 16%
CB1	DMH05	0.100	0.20	0.02	0.02	5.00	0.31	5.31	20.72 / 46.68	0.001 / 0.002	0.83 / 1.86	1.80	200	26.00	1.401	0.044	2% / 4%