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Friends Of the Rivers of Hout Bay
Tim Biggs and Willie van Wyk
2015
Site visit – 22 April 2015
Proposed solutions…
Off-channel
gravel bed
Implemented solution…
Heavily polluted low to
medium flows diverted
and pre-treated by
natural filtration
Important note:
...
Downstream litter trap…
Just below outlet: Large
school of Galaxias
roaming here!
Perfect location for a storm
water retention facility
(natural reed bed)
Draining naturally via existing
grassed ditch
Fut...
Future projects
GENERAL
Work done to date regarding
hydrodynamics of Hout Bay,
specifically looking at coastal
dispersion of river water a...
Typical dispersion of sewage
discharge during summer conditions
(surface layer)
Typical summer current pattern
Location of
marine outfall
Improved
location
RIVER WATER ABSTRACTION
What quantity of water is removed
from the Disa system?
Source: State of the Rivers report
RIVER WATER ABSTRACTION
What quantity of water is removed
from the Disa system?
Disa River Original Disa Stream
Alexandra
...
Source: CCT website
RIVER WATER ABSTRACTION
What quantity of water is removed
from the Disa system?
RIVER WATER ABSTRACTION
What quantity of water is removed
from the Disa system?
Source: State of the Rivers report
Total t...
FURTHER WORK
Some of which is in progress:
• Estuarine morphodynamics
• River flood modelling
• Marine water quality model...
A big THANK YOU to everyone who has contributed thus far !
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Friends of the rivers of hout bay COLL courtesy of THRIVE

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Friends of the rivers of hout bay COLL courtesy of THRIVE

  1. 1. Friends Of the Rivers of Hout Bay Tim Biggs and Willie van Wyk 2015
  2. 2. Site visit – 22 April 2015
  3. 3. Proposed solutions… Off-channel gravel bed
  4. 4. Implemented solution… Heavily polluted low to medium flows diverted and pre-treated by natural filtration Important note: None of the work performed to date has modified the river flow or structure in any way but it is very important that licences be obtained for any future work that might, well in advance.
  5. 5. Downstream litter trap… Just below outlet: Large school of Galaxias roaming here!
  6. 6. Perfect location for a storm water retention facility (natural reed bed) Draining naturally via existing grassed ditch Future projects
  7. 7. Future projects
  8. 8. GENERAL Work done to date regarding hydrodynamics of Hout Bay, specifically looking at coastal dispersion of river water and sewage outfall Numerical hydrodynamic model of Hout Bay
  9. 9. Typical dispersion of sewage discharge during summer conditions (surface layer)
  10. 10. Typical summer current pattern Location of marine outfall Improved location
  11. 11. RIVER WATER ABSTRACTION What quantity of water is removed from the Disa system? Source: State of the Rivers report
  12. 12. RIVER WATER ABSTRACTION What quantity of water is removed from the Disa system? Disa River Original Disa Stream Alexandra 128 Ml 126 Ml Capacity of 18Ml/day Capacity of 3Ml/day Kloofnek Treatment Plant Constantia Nek Treatment DAMS 594 Ml 925 Ml 243 Ml HOUT BAY CATCHMENT 33.8km² DAMS Woodhead Hely-Hutchinson De Villiers Victoria Compiled from CCT info and State of the Rivers report
  13. 13. Source: CCT website RIVER WATER ABSTRACTION What quantity of water is removed from the Disa system?
  14. 14. RIVER WATER ABSTRACTION What quantity of water is removed from the Disa system? Source: State of the Rivers report Total treatment capacity (Kloofnek and Constantianek) 21 000m³ /day 7 665 000m³/annum Natural runoff, Disa and Original Disa 28 500m³/day 10 400 000m³/annum Water supply system has the potential to remove 74% of natural runoff The remaining 26% is subject to uncontrolled, mostly unlicensed abstraction by riparian property owners. A hand count reveals approximately 110 properties. Let’s say 50% of those remove 1000l (1m³) per day for half the year, the abstracted volume could be in the region of 10 000 m³/annum, or about 0.1% of the annual runoff.
  15. 15. FURTHER WORK Some of which is in progress: • Estuarine morphodynamics • River flood modelling • Marine water quality modelling • Sediment transport Studies will compare the current scenario with historic and optimised / rehabilitated scenarios
  16. 16. A big THANK YOU to everyone who has contributed thus far !

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