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Case study · Stormwater network design

Stormwater network design & modelling — Saadiyat, Abu Dhabi

A new stormwater network designed from the ground up for a 10.4 ha coastal development, with two lifting stations and attenuation storage. The network was modelled in InfoWorks ICM and verified against Abu Dhabi Municipality 1-in-10-year design and 1-in-25-year check storms.

Client
Modon

Location
Saadiyat, Abu Dhabi, UAE

Scope
Network layout, hydraulic modelling, pump station checks

Tools
InfoWorks ICM

Criteria
ADM drainage design manuals

10.4 ha

Total catchment area, delineated by land use

2 pump stations

PS-01: 120 L/s · PS-02: 60 L/s at 10 m (1 duty + 1 standby)

2 × 579 m³

Underground attenuation storage cells

No flooding

Under the 1-in-10-year design storm

The challenge

A greenfield coastal site with little natural fall

With no existing drainage to connect to, the network had to be planned from first principles. The flat coastal topography limits gravity drainage, so runoff must be collected, attenuated and lifted to the outfalls, while meeting ADM requirements for a 1-in-10-year design storm and a 1-in-25-year performance check.

Catchment delineation and land-use map
Catchment delineation by land use (10.4 ha)

Our approach

Design methodology

  1. Topographical survey review and initial network layout based on site conditions
  2. Catchment delineation and runoff using the Rational Method with ADM rainfall (IDF) data, runoff coefficients and time-of-concentration factors
  3. Pipe sizing with Manning’s equation, checked against ADM velocity and gradient limits
  4. Hydraulic model built in InfoWorks ICM, including pump stations, HDPE force mains and storage cells
  5. Performance tested under the 1-in-25-year storm, network refined for the 1-in-10-year design storm, then re-verified
  6. Adequacy check of the outfalls and lifting stations for both events
InfoWorks ICM network model
Network topology in InfoWorks ICM

Results

Model results

10-year storm maximum flow plot
1-in-10-year design storm: no flooding
25-year storm flood check
1-in-25-year check: localised flooding at B-8 to B-12

Key findings

  • 10-year design: no flooding. Peak levels between IN-B10 and N-18 remain below ground.
  • 25-year check: localised, contained flooding between nodes B-8 and B-12.
  • Pumps operate within their allowable range in both events.
  • Storage stays below capacity, and Cell 1 is not used, which leaves room for optimisation.
Long section with maximum hydraulic grade line
Long section, Network C&D: maximum hydraulic grade line, 10-year storm
Pump operating points on pump curves
Pump operating points for PS-01 and PS-02 under the 10-year storm

Deliverables

  • Detailed design report with design criteria and findings
  • Calibrated InfoWorks ICM model for the 10- and 25-year events
  • Flood plots, long sections and pump operating points
  • Pump duty selection for both lifting stations

Standards applied

  • ADM Roadway Design Manual: Drainage
  • ADM Stormwater & Sub-soil Drainage Systems Design Manual
  • UPC Utility Corridor Design Manual

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