P-015
A COMPREHENSIVE GIS APPROACH TO DREDGING-RELATED
STUDIES AND DATASETS FOR THE BELGIAN COASTAL WATERS
AND THE SCHELDT ESTUARY
Natasha Blommaerf \ Frederik Roose(1), Chantai Martens<
'1\ Kenneth Cools(^
(l) afdeling Maritieme Toegang, E-mail: natasha. blommaertÇcgmow. viaanderen, be,
frederik. roose@.mow. vlaanderen. be, chantai. martens@mow. vlaanderen. be
t2>Geo Solutions NV, kenneth.cools@geosolutions.be
K eyw ords: Maritime Access, Maritieme Toegang, GIS, dredging, studies, coastal waters
A BSTRA CT
The web application ‘D ata V iew er’, developed by the Flem ish M aritim e A ccess division of
the Flem ish M inistry o f M obility and Public W orks, supports th e operation o f dredging and
environm ent-related activities in the access channels to th e Flem ish harbours. This
application enables the geographical visualisation and a lim ited analysis o f various complex
dataset types. The present database contains dredging intensity data, various hydrodynam ic
m easurem ents and density profiles on silt accretion locations. The advantages o f the D ata
V iew er are numerous: data in this central database is accessible, easy to consult and to
interpret, in relation to various dredging m onitoring and reporting activities.
Currently, the Data V iew er is only internally accessible because o f security reasons. A s soon
as the security issue is solved external third parties can register in order to log on to this site.
The Environm ent and Inform ation Portal is a JAVA based web application connected w ith an
Oracle 1 lg database and an A rc SDE 10 GIS database engine. T he GIS data are published in
the form o f web map services (W M S) and web feature services (WFS) through an Arc GIS
server 10. The visualisation o f the geographic data is im plem ented by an O penlayers
javascript library.
D red g in g In ten sity d a ta
The accessibility o f the Flem ish harbours requires continuous m aintenance dredging activities
in the navigation channels in the Belgian coastal waters and in the Scheldt estuary. The
dredged sedim ent is transported to allocated relocations sites by trailer suction hopper
dredgers. A D redging Inform ation System stores all inform ation related to the dredging and
relocation process, w hich allows the retrieval o f intensity maps o f the dredging and relocation
sites. The intensity maps, show ing the spatial distribution o f w eight and volum e o f dredged
sedim ent, are very useful for m orphological analysis in the fram ework of optim isation o f the
dredging and relocation process, environm ental m onitoring and environm ental impact
assessment.
The user interface allows querying on tim e and space. The cumulated intensity m ap is
visualised over the requested time period from 1 w eek up to several years and multiple
dredging or relocation sites in a standard colour legend.
The web based GIS view er offers standard viewing facilities, an identify tool, multiple
background layers and export features.
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Fig. 1. Visualisation of Dredging Intensity data. The pop up window allows the user to make
a search query in the dredging intensity database.
C ross-section al c u rre n t velocity m e asu re m en ts
The Belgian Coastal waters and the Scheldt estuary are subject to a tidal regime. Crosssectional hydrodynam ic m easurem ents during a tidal cycle are executed regularly w ithin the
fram ework o f the m onitoring program s along a series o f predefined transects or at request
during additional research surveys. The cross-sectional hydrodynam ic m easurem ents consist
o f a set o f consecutive acoustic recordings along a transect o f current velocity and suspended
sedim ent concentration, o f w hich discharge, and sedim ent flux through the transect can be
deduced. The data obtained during the cross sectional hydrodynam ic measurements are
im ported in the ArcSDE 10 database by a custom ised Python® script.
The user interface allows querying on time period, the location o f a cross section and on the
m easured time interval during the cycle. The queried sectional hydrodynam ic measurements
are visualised as current velocity vectors on the geographic map, indicating the current
velocity and current direction at a chosen depth. The Data Viewer is not designed to show
suspended sediment concentrations.
The web based GIS view er offers standard viewing facilities, an identify tool, multiple
background layers and export features.
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user to make a search query in the cross section current velocity measurement database.
Density profiles in silt layers
The neighbourhood o f the harbour o f Zeebrugge at the Belgian coast and the harbour o f
Antwerp in the Scheldt estuary are characterised by the presence o f a turbidity maxim um o f
fine cohesive sediments. These sedim ents accumulate in harbour basins, resulting in the
form ation o f cohesive silt layers.
The cohesive silt layers are surveyed by a dual-frequency echo sounder (210 and 33 kHz) and
by density profiles o f which the depth o f equal density layers and the nautical depth (defined
as the 1.2 t/m 3 density) can be determ ined in a certain area o f interest.
The survey results are visualised on the geographic map o f the application. All points are
labelled w ith the depth value o f the selected density values and the dual-frequency soundings.
At the m om ent o f writing, the functionality to visualise isobaths between the selected data,
was still in a developing phase. The solution for the visualisation o f the interpolation or other
geospatial processes could be delivered by the implem entation o f so called W eb Processing
services (WPS). A WPS allows the user to request a certain im age processing algorithm on
the available data. The execution o f this algorithm delivers an output w hich could be directly
returned to the client or could be saved as resource data at the server side o f the web
application.
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Fig. 3. Visualisation o f density measurements. The pop up window allows the user to make a
search query in the density measurement database.
C onclusion
The D ata V iew er provides the possibility to m anage coastal (and estuarine) inform ation in an
easy accessible and clarifying manner. M aritim e Access established a viewing portal for
various dataset types w ith GIS tools such as standard viewing facilities, an identify tool,
m ultiple background layers and m ap export features.
The Openlayers JavaScript library, w hich supports the com mon Open G eospatial Consortium
(OGC) standards, gives a pow erful geographic m ap visualisation w hich is independent o f the
im plem ented client and server.
The scalability and m aintainability o f this web based GIS view er is optim ized by using a
REST architecture in the application code. The separation between server and client allows to
develop both independently. O ther M aritim e A ccess applications, such as M atador (a search-,
view- and m etadata m anaging- portal o f GIS related data available at M aritim e Access) and
the Grid database (a search and view ing portal o f Bathymetric data), can be integrated with
the Data Viewer.
All this features makes the Data V iew er an efficient tool for various dredging m onitoring and
reporting activities. Because o f its scalable characteristics, the Data V iew er has also the
potential to becom e a powerful module for the im plem entation o f different analyses.
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