restoring ecosystem functions in a heavily disturbed estuary
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RESTORING ECOSYSTEM FUNCTIONS IN A HEAVILY DISTURBED ESTUARY
Tom Maris, Stijn Temmerman & Patrick Meire
Driving forces: - Dredging & embankments- Pollution- Climate change
loss of ecosystem functionsImpact on:- safety- economy- ecology
Schelde: disturbed estuary
Structure
Fu
nct
ion
35853
42341
28,4
20,3
32000
34000
36000
38000
40000
42000
44000
1900 1990
Su
rfac
e (h
a)
0
5
10
15
20
25
30
% i
nte
rtid
al a
rea
total surface % intertidal
Schelde: disturbed estuary
Loss of intertidal habitat loss of goods and services
5.0
5.5
6.0
6.5
7.0
7.5
8.0
1930 1950 1970 1990
ann
ual
max
. HW
(m
TA
W)
Schelde: disturbed estuary
Increasing tides: risk for floodings
slope , current speed marsh erosion
Increasing tides: habitat loss
Schelde: disturbed estuary
Structure
Fu
nct
ion
Return to pristine situationis impossible.
Sustainable solutions:
Restoring functions
Managed realignment? - Elevation often not suitable - Not always compatible with safetyplan
Flood control area: restoring safetyControlled reduced tide: restoring ecology
Schelde: solutions?
Pilot studyLippenbroek
How to restore estuarine nature in an area far below MHW?
Ecology: CRT
- Introducing estuarine ecosystem
- Tidal regime in area
- Two times a day!
Ring Dike Lowered FCA dike
FCA estuary
Outlet
polder
Concept FCA – CRT safety, ecology and a new ecosystem
Safety: FCA
- Lowered dike stretch
- Critical tides: whole storage capacity
- Only few times/year!
Ring Dike Lowered FCA dike
CRT estuary
Outlet
Inlet
polder
Lippenbroek
1: Ring Dike
2: FCA dike
3: Inlet sluice
4: Outlet sluice1
23
1
4
1
1
Management scenario Lippenbroek
10 ha of tidal nature developping since March 2006
Pilot project Lippenbroek
Pilot project Lippenbroek
10 ha of tidal nature developping: May 2008
0
1
2
3
4
5
6
7
7/04 12/04 17/04 22/04 27/04 2/05 7/05
date
leve
l (m
TA
W)
Schelde (De Plaat)
Lippenbroek
0
1
2
3
4
5
6
7
7/04 12/04 17/04 22/04 27/04 2/05 7/05
date
leve
l (m
TA
W)
Lippenbroek
Schelde (De Plaat)
0
1
2
3
4
5
6
7
7/04 12/04 17/04 22/04 27/04 2/05 7/05
date
level
(m T
AW
)
Lippenbroek
Schelde (De Plaat)
Introducing macrotidal regime
Reduction of high water level by 3 meter No reduction of spring – neap variation
Introducing macrotidal regime
Intertidal habitat development
Tide - Sedimentation
-2
0
2
4
6
8
10
12
14
0 20 40 60 80 100
inundation frequency (%)
accr
etio
n r
ate
(cm
/yea
r)
Lippenbroek
"De Plaat"
Tidal marsh
Tidal flat
?
?
?
Tide - Sedimentation
Tide - Sedimentation
-2
0
2
4
6
8
10
12
14
0 20 40 60 80 100
inundation frequency (%)
accr
etio
n r
ate
(cm
/yea
r)
Lippenbroek
"De Plaat"
Low
Mean
High
Sediment(cm)
10
00
00
20
00
00
Spring 2006 Winter 20081
00
00
02
00
00
0
Spring 2006 Winter 2008
10
00
00
20
00
00
spring 2006 Winter 2008
High
Mean
Low
Aquatic species+ insects
Aquatic species + insects
Terrestric species + Insects+ others
Max densityin fine sediments200000 / m²
Zoobenthos
0
5
10
15
20
Colonising species (40)Low inundation frequency:
30 species
- Wetland + ruderal species
- Salix and Phragmites potentially dominant
Averaged inundation frequency:
27 species
- Ruderal + wetland species
- Salix, Phragmites, Typha: pot. dominant
- High inundation frequency:
10 species
- typical wetland species
- Typha potentially dominant
Phragmites australis
Ranunculus repens
Salix sp.
Lythrum salicaria
Typha latifolia Iris pseudacorus
Callitriche sp. Veronica beccabunga
Alisma plantago-aquatica
Vegetation: colonisation of bare sites
Water quality
0
25
50
75
100
125
150
175
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
time (hour)
oxy
gen
(%
sat
)
STAGNANT
STAGNANT
INFLOW OUTFLOW
Water quality: oxygen
0
2
4
6
8
10
9 10 11 12 13 14 15 16 17 18 19 20 21 22time (hrs)
DS
i (m
g/l
SiO
2)
Lippenbroek estuary
Inflow Outflow
Water quality: Silica
DSi delivery on 3/7/2006
02468
101214
16/0
5/20
06
3/07
/200
6
11/0
9/20
06
25/1
0/20
06
20/0
3/20
07
21/0
3/20
07
4/06
/200
7
5/06
/200
7
1/10
/200
7
DS
i (m
g/l
SiO
2)
-10
0
10
20
30
40
DS
I (k
g S
iO2)
Si inflow conc. Si retention
Water quality: Silica
Delivery when DSi is limiting
Water quality: Nitrogen
0
20000
40000
60000
80000
16/0
5/20
06
3/07
/200
6
11/0
9/20
06
25/1
0/20
06
20/0
3/20
07
21/0
3/20
07
4/06
/200
7
5/06
/200
7
1/10
/200
7
volu
me
(m³)
0
5
10
15
20
TDIN
(kg)
tidal volume N retention
On average 1 kg N retention per ha per tide
???
Ring dike
Overflow dike
CRT
FCA-CRT: sustainable?
Sedimentation
Flattening of the area
Changing inundation frequencies: decrease of accretion?
2.25
2.50
2.75
3.00
3.25ja
n 06
apr
06
jul 0
6
okt
06
jan
07
apr
07
jul 0
7
okt
07
jan
08
apr
08
datum
ho
og
teli
gg
ing
(m
TA
W)
S2
S4
S5
S7
S9
S10
S4
2.40
2.50
2.60
2.70
2.80ja
n 06
apr
06
jul 0
6
okt
06
jan
07
apr
07
jul 0
7
okt
07
jan
08
apr
08
jul 0
8
okt
08
jan
09
apr
09
jul 0
9
datum
ho
og
teli
gg
ing
(m
TA
W)
S4
???
future
date
Ele
vati
on
(m
TA
W)
Development of cross-section 1 (main channel)
0,5
1
1,5
2
2,5
3
3,5
0 5 10 15 20 25
Distance along cross-section (m)
Ele
vati
on
(m
TA
W)
T0
T1
T2
Erosion
Tidal marsh restoration in area below MHW is possible
Tidal regime and sedimentation can be tuned
Sedimentation rate can be reduced to preserve storage capacity
Sedimentation rate can be maximased to prepare a low site for succesful managed realignment
Lippenbroek conclusion
Tidal marsh restoration in area below MHW is possible
Tidal regime and sedimentation can be tuned
Tidal marsh restoration in area below MHW is possible
Tidal regime and sedimentation can be tuned
Sedimentation rate can be reduced to preserve storage capacity
Tidal marsh restoration in area below MHW is possible
Tidal regime and sedimentation can be tuned
Sedimentation rate can be reduced to preserve storage capacity
Ready for the big work?
Thanks
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0 2 4 6 8 10 12Time (hour)
Wa
ter
lev
el
(m T
AW
)
Polder
Estuary
sluice 4.7
Start inflow
stagnant
HW Maximum inflowStop inflow Start outflow
Introducing macrotidal regime
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