sigmaplan ‘safety & ecology’ creating a sustainable estuary of the schelde patrik peeters...
TRANSCRIPT
Sigmaplan ‘Safety & Ecology’
Creating a sustainable estuary of the ScheldePatrik Peeters
18/05/10
355 km21.863 km2
10,5 milion people
Estuary of the Schelde
Storm surge in 1976
Schelde
Durme
Sigmaplan anno 1977
- Dike strengthening & heightening- Flood Control Area (FCA)
ScheldeFCA
1
2
3
4
Ring dike Lowered levee
1
2
3
4
Working principle of a FCA
90 m 90 m
54 m 54 m 54 m120 m
123 m
Sigmaplan anno 1977
- Flood barrier
Sigmaplan anno 2005
• No longer 1 flood protection level – Flood risk assessment• Taking into account possible breach formation• Combination of dike strengthening and FCA• Based on a SCBA
Water management today: limit the damage
Water level
1. Probability 2. Flood modeling
3. Damage calculations
4. Risk = Σ Probability x Damage
Flemish Risk Methodology
Sigmaplan anno 2005
• Adressing ecological needs• System approach• Habitat approach• Species approach
• More space for the estuary• Non-tidal wetlands• Combining FCA with
• agriculture• non-tidal wetland• a Controlled Reduced Tide (CRT)
Pilot Project LIPPENBROEK
• Flood Control Area (FCA) with a Controlled Reduced Tide (CRT)
• Ring dike• Overflow dike• Inlet structure (high sill)• Outlet culvert (low sill, flapped)
• Semi-diurnal water exchange• Creation of intertidal habitat
with inundation characteristics similar to natural conditions, ie. profound springtide/neap tide cycle
Outlet (low sill) and inlet (high sill)
Springtide/neap tide cylce
• Reduced tide• Stagnante phase
Pilot Project LIPPENBROEKINLET (CRT side)
OUTLET (river side)
OUTLET (CRT side)
Overflow dike
Freshwater Intertidal HabitatCREEK
RESERVOIR
SHALLOW POOL
ready for colonisation, nutrient cycling, …
Discharge measurements
• At the inlet• Rectangular section• Sharp-crested weir
• At the inlet• By ADCP• Head-discharge relations
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.5 5 5.5 6 6.5
Upstream water level (m AD)
Infl
ow
dis
ch
arg
e (
m³/
s)
Discharge measurements inlet sluice 1
Discharge measurements inlet sluice 2
Discharge measurements inlet sluice 3
sharp-crested weir formulas for Inlet 1, 2 & 3
Discharge measurements
• At the outlet• Rectangular section• Broad-crested weir• Trash rack
• By ADCP• Validation of continuously measured
flow velocities and water levels
Discharge measurements
• At the outlet
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
16/11/08 20:00 17/11/08 14:00 18/11/08 08:00 19/11/08 02:00 19/11/08 20:00
Ou
tflo
w d
isch
arg
e (m
³/s)
Q measurement
Q validated
Q predicted
Discharge measurements
Sediment sampling
• Each in- and outflow• At in- and outlet• Tidal sampling• SSC in laboratory (mg/l)
• At distinguished moments: detailed sampling
• Turbidity measurements (NTU)
Sediment sampling
• Relations between Q (m³/s), SSC (mg/l) et turbidity (NTU)• Eg. at the inlet:
y = 21.824x + 20.975
R2 = 0.7608
0
50
100
150
200
250
0 1 2 3 4 5 6 7
Inflow discharge (m³/s)
Su
spen
d S
olid
Co
nce
ntr
atio
n (
mg
/l)
²
0
1
2
3
4
5
6
7
1 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 85 89 93 97 101
Infl
ow
dis
ch
arg
e (
m³/
s)
0
50
100
150
200
250
Su
sp
en
de
d S
oli
d C
on
ce
ntr
ati
on
(m
g/l
)
Discharge
SSC
15/05/06
11/09/06
04/12/08
19/10/06
30/08/07
01/10/07
Water and sediment balance
Inflow Peak discharge (m³/s)
Duration (hr:min)
Volumes (m³)
SSC at peak flow (mg/l)
Mean tide 3.5 2:25 18.000 97 Neap tide 1.0 1:55 5.000 43 Spring tide 5.4 2:45 28.000 139
Mean discharge (m³/s)
Duration (hr:min)
Volumes (m³)
SSC (mg/l)
Leakage (inflow through tide gate)
0.5 6:40 1.000 15 - 54
Outflow Peak discharge (m³/s)
Duration (hr:min)
Volumes (m³)
SSC (mg/l)
Mean tide 2.5 5:30 19.000 15 - 54 Neap tide 1.1 4:50 7.000 15 - 54 Spring tide 3.3 5.45 29.000 15 - 54
Sediment balance10³ kg/year Incoming
sediment Outflowing sediment
Remaining sediment
Sediment entrapment (%)
1300 Mean outflow 330 970 75 1300 - Sigma 80 1220 94
2006
1300 + Sigma 570 730 56 1300 Mean outflow
(2006-2008) 380 920 71
1550 Mean outflow 390 1160 75 1550 - Sigma 100 1450 94
2007
1550 + Sigma 680 870 56 1550 Mean outflow
(2006-2008) 450 1100 71
1300 Mean outflow 470 830 64 1300 - Sigma 120 1180 91
2008
1300 + Sigma 820 480 37 1300 Mean oufflow
(2006-2008) 550 750 58
Improving connectivity
• Between estuary and FCA, non-tidal wetlands, tributaries, …
• Enhancing (fish) migration• Fish passages• Fish-friendlier tide gate designs• Culvert adjustments
Fish immigration
Fish emigration
INLET
OUTLET
OUTLET
Improving connectivity
Tide gate of outlet Lippenbroek
• 1.80m x 1.80m• Double hinged from above• Small opening at low flows• Turbulent at high flows, but
with sufficient opening
Side-hinged “Pet Door”
Mono-hinged “Pet Door”
