This document discusses methods for reducing salt intrusion through shipping locks using air-bubble and water screens or sills. It summarizes field experiments conducted at the Stevin shipping lock where sensors measured salt levels with and without these screens. Without screens, salt freely intruded into and left the lock during opening and closing. Screens significantly reduced this salt exchange. The best performing screens combined an air-bubble screen on the seaward side with a sill on the landward side, reducing typical salt transmission through the lock to 15% of unhindered levels. Equations are presented explaining the theoretical hydraulic mechanisms by which screens impede lock exchange flows and salt intrusion.

1. Rob Uittenbogaard (Deltares, Netherlands)
John Cornelisse (Deltares, Netherlands – retired)
Ken O’Hara (Flowthrough Ltd UK)
Water & Air-Bubble Screens Reducing Salt Intrusion
Through Shipping Locks
Commissioned by Rene Boeters & Hans van Pagee
Rijkswaterstaat, the executive agency of the Ministry of Infrastructure and the
Environment
IAHR – 2015 Session 10K

2. Existing Locks:
1. Delfzijl
2. Lauwersoog
3. Harlingen
4. Kornwerderzand
5. Den Oever
6. Den Helder
7. IJmuiden
8. Spaarne
9. Schiedam
10. Spijkenisse
11. Stellendam
12. Terneuzen
13. Krammersluis
14. Bergse Diepsluis
14. Kreekraksluis
15. Antwerpen
Toekomst ?
16. Volkeraksluis
17. Dintelmond
18. Beneden Sas1
16
18 17
2
3
4
56
7
8
9
10
11
12
15
14
13
Shipping Locks Separating Salt from Fresh Water
Water
Transport Sea ↔ Inland Waters
Total 267 kg salt / s excl. IJmuiden (1070) & Terneuzen (52)
Rhine: 270 - 400 kg salt / s
Terneuzen
IJmuiden
2

3. Our Test Site: The Stevin Shipping Lock
14m Wide
148m Long
4.7m Deep
Lock GatesTraditional
Air-Bubble Screen
Slots
3

4. Lock
Seaward
Port
Lake IJssel
Water
PumpΔ- Bubble Screen
Δ- Water Screen
Δ- Bubble Screen
Δ- Sill
S - Bubble Screen
CTD’s
Ponton &
CTD’s
Stevin Ship Lock – Installation by Deltares
S - Bubble Screen
Ponton &
CTD’s
Water
Pump
Landward
Port
10m10m

5. In and Outside Lock : 7*5 CTD Strings - Top Three Floating
5

6. 6
Observed Sequence of Unhindered Salt Intrusion into the Lock

7. 7
Observed Sequence of Unhindered Salt Intrusion into the Lock

8. 8
Observed Sequence of Unhindered Salt Intrusion into the Lock

9. 9
Observed Sequence of Unhindered Salt Intrusion into the Lock

10. 10
Observed Sequence of Unhindered Salt Intrusion into the Lock

11. 11
Observed Sequence of Unhindered Salt Intrusion into the Lock

12. 12
Observed Sequence of Unhindered Salt Intrusion into the Lock

13. 13
Observed Sequence of Unhindered Salt Intrusion into the Lock

14. 14
Observed Sequence of Unhindered Salt Intrusion into the Lock

15. 15
Observed Sequence of Unhindered Salt Intrusion into the Lock

16. 16
Observed Sequence of Unhindered Salt Intrusion into the Lock

17. 17
Observed Sequence of Unhindered Salt Intrusion into the Lock

18. 18
Observed Sequence of Unhindered Salt Intrusion into the Lock

19. New Design of Air-Bubble Screens Replacing Perforated Pipes
19

20. Air-Bubble Screen - 10m outside Seaward Gate
Lnf
Lock Floor
Sea Water Brackish
I
II
III
V
IV0
Seaside Port Lock Side
Seaward Lock Gate : Freshwater Screen Shielding Air-Bubble Screen
• 2D Jet Shields Vulnerable Air-Screen Base
• Buoyant Jet
• Fresh-Water Entrainment to Lock
Freshwater Screen
20
1.6 m³/s
0.05m slot
2.3 m/s 2D-Jet

21. 21
Water & Air-Bubble Screen Reduces Salt Intrusion into the Lock

22. 22
Water & Air-Bubble Screen Reduces Salt Intrusion into the Lock

23. 23
Water & Air-Bubble Screen Reduces Salt Intrusion into the Lock

24. 24
Water & Air-Bubble Screen Reduces Salt Intrusion into the Lock

25. 25
Water & Air-Bubble Screen Reduces Salt Intrusion into the Lock

26. 26
Water & Air-Bubble Screen Reduces Salt Intrusion into the Lock

27. 27
Water & Air-Bubble Screen Reduces Salt Intrusion into the Lock

28. 28
Water & Air-Bubble Screen Reduces Salt Intrusion into the Lock

29. 29

30. 30
Observed Sequence of Unhindered Salt Leaving the Lock

31. 31
Observed Sequence of Unhindered Salt Leaving the Lock

32. 32
Observed Sequence of Unhindered Salt Leaving the Lock

33. 33
Observed Sequence of Unhindered Salt Leaving the Lock

34. 34
Observed Sequence of Unhindered Salt Leaving the Lock

35. 35
Observed Sequence of Unhindered Salt Leaving the Lock

36. 36
Observed Sequence of Unhindered Salt Leaving the Lock

37. 37
Observed Sequence of Unhindered Salt Leaving the Lock

38. 38
Observed Sequence of Unhindered Salt Leaving the Lock

39. 39
Observed Sequence of Unhindered Salt Leaving the Lock

40. 40
Observed Sequence of Unhindered Salt Leaving the Lock

41. 41
Observed Sequence of Unhindered Salt Leaving the Lock

42. 42
Observed Sequence of Unhindered Salt Leaving the Lock

43. Air-Bubble Screen – inside Lock 10m before Landward Gate
Lnf
Lock Floor
Lock Water Fresh Water
I
II
III
V
IV0
Lock Landward Port
• Sill Shields Vulnerable Air-Screen Base
• Sill Reduces Lock Depth in Exchange Flow
Sill
43
Landward Lock Gate : Sill Protecting Air-Bubble Screen
1.2 m Sill Height
Landward Port

44. 44
Sill & Air-Bubble Screen Reduces Salt Intrusion into the Lock

45. 45
Sill & Air-Bubble Screen Reduces Salt Intrusion into the Lock

46. 46
Sill & Air-Bubble Screen Reduces Salt Intrusion into the Lock

47. 47
Sill & Air-Bubble Screen Reduces Salt Intrusion into the Lock

48. 48
Sill & Air-Bubble Screen Reduces Salt Intrusion into the Lock

49. 49
Sill & Air-Bubble Screen Reduces Salt Intrusion into the Lock

50. 50
Sill & Air-Bubble Screen Reduces Salt Intrusion into the Lock

51. 51
Sill & Air-Bubble Screen Reduces Salt Intrusion into the Lock

52. 52
Sill & Air-Bubble Screen Reduces Salt Intrusion into the Lock

53. 53
Sill & Air-Bubble Screen Reduces Salt Intrusion into the Lock

54. 54
Sill & Air-Bubble Screen Reduces Salt Intrusion into the Lock

55. 55
Sill & Air-Bubble Screen Reduces Salt Intrusion into the Lock

56. H
D
h
ρ− ρ−
ρ+ρ+
g
U
δ =
h
D
2
 
= − 
′  
H
U D D
F
H Hg H
Lock Exchange Flow – The Classical Theory – Extended by Shin et al., 2004
( )1
2
g g
ρ ρ
ρ ρ
+ −
+ −
−
′ =
−
56
Reduced Gravity
Internal Froude
Number
Intrusion
Thickness
δ FH
No Loss 0.5 0.5
Max Loss 0.347 0.527

57. 57
Arrival Closed Gate Leave Lock
Unhindered Unhindered
Averages of Salt Mass ÷ Time Observations in Shipping Lock
100% Exchange 100% Exchange

58. 58
Reduction of Salt Mass Exchange ÷ Unhindered

59. ( )
1
3
air
air
g q
Fr
g H
=
′
Lock Exchange Flow – Reduced by Air-Bubble Screens (Abraham et al., 1962)
Salt-Mass Exchange Hindered by Bubble Screen
Salt-Mass Exchange, Unhindered
η =Salt-Transmission
Ratio
Salt-Mass Exchange with Lock Doors Opened
Froude – Air Number
qair is Specific Air Flux [m3/s.m]
( )1
2
g g
ρ ρ
ρ ρ
+ −
+ −
−
′ =
−
Reduced Gravitational Acceleration
59

60. Summary of Best Conditions for Air-Bubble & Water Screens or Sill

61. 61
Theory Reduction Salt Transmission Through Shipping Locks
15%
15%

62. 62
The End of my Presentation
Thank You !
Questions?
Mail rob.uittenbogaard@deltares.nl