Keesstra riparian forest Poland

Assessment of riparian forest
management impact on sediment
yield in two headwater catchments
in SW Poland.
By:
Saskia Keesstra Wageningen University (Netherlands)
Elena Kondrlova, University of Nitra (Slovakia)
Agnieszka Czajka, University of Silesia (Poland)
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Background (1)
• Large-scale flooding in Eastern Europe
forms dramatic constraints for the future
economic development
• Hinterland delivers:
– excess of water: flood risk.
– large quantities of sediment: accumulates in
reservoirs or problems in fairway.
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Background (2)
• Aim larger framework: To understand processes
of water and sediment generation in headwaters
of major waterways.
• We looked at these processes in meso-scale
catchments:
– Meso- scale is :
– large enough to be representative of processes
involved
– small enough to be homogeneous and thus allow
unambiguous results.
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Research framework
• Meso-scale catchment of Nysa Szalona in
SW Poland:
– interaction between land use and sediment
and water delivery.
– The determining factors influencing the
sediment and water delivery from this mesoscale headwater catchment (this study) by
modelling sediment yield and discharge
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Aims of this study (1)
• To assess influence of
– Channel geomorphology and vegetation
– Riparian zone width
on
– Sediment retardation
– Flood retention
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Aim (2)
• To calculate possible ecologically friendly solutions
to reduce:
–sediment delivery to the main channel
–retard the flood wave
• These scenarios were assessed on effectiveness
with a GIS-based sediment delivery model and a
simple rainfall-runoff model.
Background
Aims
Study area
Methodology
Study area
• Nysa Szalona:
South western Poland,
foothills of
Carpathians, 350km2,
• Two sub-catchments
of the Nysa Szalona
– Sadowka and Upper
Nysa Szalona
Results
Conclusions Outlook
• Nysa: (23km2):
channel largely
natural
• Villages further
from channel.
60
50
40
[%]
• Sadowka (43km2):
channel largely
channelised with
concrete or brick
walls and/or
channel bed.
• Villages largely
around channel
30
20
10
0
nysa
fields
sadowka
forest
pasture
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Methodology
– Field campaign:
• Geomorphology of the channel
• Vegetation and ecology of the riverine habitat
• Channel divided in sections on the basis of
similarity, to construct current situation.
– Modelling current land use and scenarios
• Sediment delivery: watem/sedem
• Discharge: SWAT
Methodology
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Characterization of channel and
riparian zone (1)
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Characterization of channel and
riparian zone (2)
• 19 categories
• Each category had several (2-5) ‘training
sets’ (cross-section/vegetation
mapping/geomorphological mapping).
• These were used to map the rest of the
channel, without extensive measurements
• Result: map of total river channel with
riparian zone.
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Models
• For the characterization of the two subcatchment and to run scenarios for land-use:
• Sediment delivery: WaTEM/SEDEM model
• Hydrology: SWAT
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
WaTEM/SEDEM
• RUSLE based sediment delivery model with
good sediment transport functions
• Input:
–
–
–
–
DEM
Soil map
Erosivity estimate (R-factor)
Parcel map (extra sediment retardation on the border
from one field to another).
– Land-use map
– Problem: very little info on actual sediment delivery.
– Therefore only used for qualitative comparison on the
two basins and the scenarios.
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Model Runs
• 1: Current situation
• 2: Current land use + concrete channel and
riparian zone
• 3: Current land use + forested riparian zone
• 4: All catchment under forest
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Results WaTEM/SEDEM (1)
Sadowka
[ton/ha/y]
Current land use
Nysa
[ton/ha/y]
Fields: 39%
Forest: 34%
4.6
Rip: forest
4.5
5.2
Channelized
4.7
5.4
All forest
3.1
1.7
Land use
Fields: 57%
Forest: 26%
5.3
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Results WaTEM/SEDEM (2)
• Sediment retardation (WaTEM/SEDEM)
– Positive effect of a forested riparian zone.
– However: we feel the Watem/SEDEM cannot
model channel related changes satisfactory.
– Therefore: adapted LAPSUS model in the
making.
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Hydrological differences
10
10
k-value Nysa = 11.5 days
1
Q [mm]
Q [mm]
k-value Sadowka = 7.0 days
1
0.1
22-04-08
12-05-08
Sadowka
Nysa
Time to peak 9 hours
6 hours
%peak Q
24%
19%
22-apr-08
02-04-08
2-apr-08
13-03-08
13-mrt-08
22-02-08
22-feb-08
02-02-08
2-feb-08
13-01-08
13-jan-08
0.1
24-12-07
24-dec-07
0.01
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
SWAT (discharge) results
1.4
1.2
Sadowka
Q [m3/s]
1
Q_observed
current
all forest
riparian forest
channelized
0.8
0.6
0.4
0.2
0
2-2-2008
12-2-2008
22-2-2008
3-3-2008
13-3-2008
23-3-2008
2-4-2008
• Differences resulting from changes in the riparian zone
limited, although has positive effect on Q
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
1D-example of benefits of increasing
Mannings n: river restoration
0.14
M a n n in g s n = 0 . 0 4 8
M a n n in g s n = 0 . 2
0.12
0.10
0.08
0.06
0.04
0.02
0.00
0
20
40
60
80
100
120
• Conceptual model indicates SWAT inability to model
effects of river restoration
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Conclusions
• Sediment retardation (WaTEM/SEDEM)
– Positive effect of a forested riparian zone.
– However: we feel that WaTEM/SEDEM cannot model
channel related changes satisfactory.
• Flood retention:
– Major influence on flood: catchment form
– Also here SWAT does not model scenarios
satisfactory.
• Therefore: adapted LAPSUS model in the
making.
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Outlook
• Adapted LAPSUS model: LAPSUS-D in
the making.
• With this model:
– meso-scale catchment (40-400 km2)
– hydrological component
– daily time-step
– only needs commonly available data (DEM,
soil map, daily P/Q, land use map)
– use water discharge as calibration source
Background
Aims
Study area
Methodology
Results
Conclusions Outlook
Modelled and TRUE discharge at outlet
m3/d
Current status of model
development
6
4
3
2
•1
0
First focusing on calibration water discharge
because:
–
–
Available daily data
Surface runoff is main source of water erosion
Currently discharge is modelled with fairly high
accuracy.
1
8
15
22
29
36
43
50
57
64
71
78
85
92
99
106
113
120
127
134
141
148
155
162
169
176
183
190
197
204
211
218
225
232
239
•5
model output
•
TRUE
Next step to check in other catchments and
include sediment yield
Questions?