Urban Stormwater Design - Report

This report covers the design of urban stormwater systems including roof gutter and downpipe design, property drainage design, and calculations for catchment area, rainfall intensity, and discharge. The report references AS 3500.3 and includes diagrams and calculations.

Running head: URBAN STORMWATER DESIGN 1
Urban Stormwater Design
(Report)
Name
Institution

URBAN STORMWATER DESIGN 2
Urban Stormwater Design
Assignment 1
1. Attached: Diagram of the roof footprint, driveway, and paved areas for each lot.
2. Size and layout of roof gutter and downpipe.
Calculations – Gutter Desin.
i. Catchment area/Roof Area = Plan Area = 150m2 (Ah)
Rise in 1m = 1 x 150 (Av)
Total Catchment Area = Ah + Av/2
= 150+ 150
2
= 225 m2
i. Design 5 min duration, 100 year ARI rainfall intensity
= Assume, 214 – Sydney
ii. Roof ‘Average’ slope;
= 23o
iii. From Design Chart 4.A3 - AS 3500.3, 2003; the following are the
recommended designed gutters (box gutters) – All units in mm.
Diameter Number Req. Number Used Gutter Area Gutter Width Gutter Depth
90 7.75 8 8661 125 70
100 6.11 7 9740 140 70
150 2.45 3 20777 200 105
225 0.98 1 53942 330 165
300 0.51 1 53942 330 165

URBAN STORMWATER DESIGN 3
Calculations – Design of Downpipes
Assumed Locality = Sydney
Roof Catchment Area = 150m2
Rainfall Intensity = 225 mm/hr
Proposed Gutter Gradient = 1: 200
Gutter Length = Approx. 20m,
Selected Gutter Width = 140mm,
Gutter Depth = 70, Gutter Area = 9740
Required Downpipe Size From Design Chart 4.A3 - AS 3500.3, 2003;
= 100 mm x 50 mm, 90mm dia. 100mm x 75 mm.
Total continuous measures overflow capacity (L/s/m)
= 0.5
Total continuous measures overflow capacity (L/s)
= 50
Total dedicated measures overflow capacity (L/s)
= 0.5
Overflow volume (L/s) = 5.4 Total overflow capacity = 5.5 (Overflow measures adequate for
selected downpipe)
3. Property Drainage Design;
i. Catchment Area Characteristics;
Hydraulic Grade Level (HGL) = 1.2 - A
Slope = C h ange∈GL
C h ange∈IL
= 1

URBAN STORMWATER DESIGN 4
Runoff coefficient (C), From AS 3500.3, 2003;
Gradient > 0.05, steep terrain, Terrain type – residential areas and light industry;
therefore Runoff coefficient = 0.8.
ii. Rainfall intensity = 225 mm/hr
iii. Discharge from catchment area,
Qdes = 2.8 x C x I x A
= 2.8 x 0.8 x 225 x 5996/100000
= 302.1984 L/s
iv. Drainage Sizing,
Q = 1000 x (A x (R) 0.67 x (S) 0.5 N) / N
302.1984 L/s = 1000 x (A x (R) 0.67 x (S) 0.5 N) / N
AS 3500.3, 2003;
Available Drainage Diameter, = 525 mm,
Flow = 356.428,
Theoretical drainage Dia in mm = 168,
Flow velocity (m/s) = 8.96
Catchment Area flow, 302.1984 L/s, OK.

URBAN STORMWATER DESIGN 5
References
STANDARDS AUSTRALIA. (2015). Australian Standard ™ Plumbing and drainage Part 3:
Stormwater drainage. AS 3500.3 .
VICTORIAN BUILDING AUTHORITHY. (2015). Australian/New Zealand Standard Plumbing
and drainage - Part 3: Stormwater Drainage. AS 3500.3 .