gis sediment assignment western scheldt
DESCRIPTION
suitability map for the dumping of sediment in the Western ScheltTRANSCRIPT
GIS sediment assignment
Authors: Cosmin Parlog,Floris van den Hurk
Education: Water Management
Course: CU08656 -Water system analysis
Lecturer: Alco Nijssen
Date: 28.05.2013
Place: Vlissingen, the Netherlands
Contents1. Introduction.......................................................................................................................................1
2. Approach and Methodology..............................................................................................................2
3. Results...............................................................................................................................................4
4. Discussion & Conclusion....................................................................................................................9
1. Introduction
The Western Scheldt is an estuary located in the most southern part of the Dutch coast. Since the
harbour of Antwerp is connected to this estuary, a lot of shipping activities take place. For this
reason the main channel is kept intact with dredging activities. The dredging process in the Western
Scheldt is a continuous process in which a yearly amount of 7 million cubic meter of sand are
dredged. All the dredged material has to be dumped and because the current dumping sites are full,
there is the need to find new relocation sites in the Western Scheldt, where environmental impact is
the lowest. The aim of this report is to find new suitable dumping locations for the dredged
sediments, by preforming a spatial analysis with the help of GIS.
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2. Approach and Methodology
To start with, a cartographic model was made, which is a graphic representation of data and the
analytical procedures used in this assignment. The analytical procedures, in this case, are the
functions reclass and overlay that were used in GIS to create a map that portrays desired. Figure 1
show the cartographic model. The final product is a map showing the most suitable dumping
locations. To be able to assess which suitable dumping locations are available seven preconditions
were chosen, to which the final map must comply. These requirements are listed below:
1. Sediments should not be dumped at locations with high species richness;
2. Dumping locations shouldn’t overlay fishing grounds;
3. No high biomass should be present at the new dumping sites;
4. Former dumping areas must be avoided;
5. Dumping sediments may not interfere with dredging activities;
6. Sediments must stay in the water body;
7. To avoid erosion the velocity of the water at the dumping locations must be as low as
possible;
For each of these requirements a corresponding Boolean map was made, using the reclass function
in GIS. Each Boolean map contains the values one and zero. The value one indicates a positive
possibility to dump sediments, whereas zero indicates that no dumping activities should take place.
Consequently the seven Boolean maps were overlaid to create the map BestDumpOK, in which the
positive dumping locations meeting all seven requirements are shown.
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3. Results
The map species is chosen to evaluate and analyse the species richness. The map showed six degrees
of species richness present in the estuary. In the Boolean map speciesOK, made from the map
species, the acceptable degrees of species richness have the value one for very poor, poor and quite
poor (see figure 2).
Figure 1 Topographic result of reclassifying the map species.
The map shrimp shows current locations where fishing activities for shrimp take place. In the
Boolean map shrimpOK, made from the map shrimp, the value one is given to locations where there
are no fishing activities.(see figure 3.)
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Figure 2 Topographic result of reclassifying the map shrimp.
The map biomass portrayed six degrees of biomass concentration. In the Boolean map biomassOK,
made from the map biomass, the acceptable degrees of biomass have the value one for very low,
low and quite low biomass concentration.(see figure 4)
Figure 3 Topographic result of reclassifying the map biomass.
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The map dumping areas shows the location of current dumping sites. In the Boolean map dumping
areasok , made from the map dumping areas, the value one is given to locations where there are no
current dumping sites.(see figure 5)
Figure 4 Topographic result of reclassifying the map dumpingareas.
The map dredging displays the current locations where dredging activities are taking place. In the
Boolean map dredginOK, made from the map dredging, the value one is assigned to the values
consistent with no dredging areas(see figure 6).
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Figure 5 Topographic result of reclassifying the map dredging.
The map Scheldt displays the boundary of the Scheldt estuary. In the Boolean map Scheldeok, which
was made from Scheldt, the value one is given to the data Water (see figure 7).
Figure 6 Topographic result of reclassifying the map schelde
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The map velocity illustrates the values of the velocity of the water in the estuary. In the Boolean map
velocityok, made from the velocity map, the value one is given for velocities smaller than 0.5 meter
per second (see figure 8).
Figure 8 Topographic result of reclassifying the map schelde
All the Boolean maps are put together in order to create the BestdumpOK map. This map displays
the best suitable dumping sites with the colour cream. (see figure 9)
Figure 9Topographic result of reclassifying the map schelde
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4. Discussion & Conclusion
The final area suitable for the sediment unloading is 281.01 hectare. Taking in account that the
average depth of the Western Scheldt is 6 meter a rough estimate of the total volume of available in
these areas is 16860734.82 meter cube. For a more accurate calculation each specific area can be
multiplied by its depth.
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