Workshop sur l’environnement marin et développement durable: quels enjeux pour demain? A l’EST Essaouira, du 20 au 21 décembre 2013
Remote Sensing and GIS Contribution to the Monitoring of the Marine Environment and of Flooding Hazards in the Coastal Areas of W- Morocco Prof.Dr.habil.Barbara Theilen-Willige, December 2013 with support of the GeRiSa-Team (Gestion des Risques de l’Environnement dans la Région de Safi, Maroc) Ait Malek, H(2), Ait Ougougdal, M.(2), Boumaggard, E(2), Buchert, W.(1), Chaibi, M.(2), Charif, A.(2), El Bchari, F.(2), Löwner, R.(1), Müller, J.(1), Nakhcha, C.(2), Ridaoui, M.(2), Theilen-Willige, B.(1), (1) TU Berlin, Institute of Applied Geosciences, Ernst-Reuter-Platz 1, 10587 Berlin, Germany (2) Université Cadi Ayyad, Faculté Polydisciplinaire, Équipe de Géomorphologie, Environnement et Gestion du Littoral (GEGEL), B.P: 4162, Sidi Bouzid, 46000 Safi, Maroc
Introduction
The quality , data amount and information content of GeoInformation Systems (GIS) dealing with natural hazards and vulnerability assessment has increased considerably during the last decade. Meanwhile many countries have implemented such a GIS for the public use, whereby satellite imageries before and after disasters form important layers within these GIS. Aim of this study is a contribution to a flooding hazard assessment in W-Morocco using remote sensing and GIS tools. A transparent and standardized method is presented using mainly free available, existing data for contributing to a GeoInformationSystem (GIS) integrated data base.
Université Cadi Ayyad Cadi Ayyad University, Faculty Polydisciplinary of Safi, Safi, Morocco
TU Berlin Institute for Applied Geosciences Berlin, Germany
Moroccan-German Programme of Scientific Research Environmental Risk Management in the Region of Safi, Morocco
Start of the project March 2013
Workflow
Digital Image Processing of RapidEye and LANDSAT-Data • RGB • NDWI-Wasser-Index for soil moisture detection • NDVI-Vegetationsindex for vegetation anomaly detection • Principal Component, classifications • Filter techniques (Morphologic Convolution)
GIS integrated Evaluation of Satellite Data • Extraction of areas with higher soil moisture • Lineament analysis • Change detection • Weighted Overlay
Integration and Combination of Geodata
. Integration of geophysic, geologic, geomorphologic and soil data
. Digital Elevation Data (DEM) . Vegetation, land use, infrastructure
Satellite Imageries for the Monitoring of Flooding Hazards Les Images Satellites pour l’Observation et le Contrôlant de Hasards Naturels
RapidEye
LANDSAT
Spatial resolution: 5 meters
Spatial resolution:15 – 30 m
QuickBird Spatial resolution: 0,61 – 2,8 meters
MODIS ASTER (TIR) ASTER (SWIR) ASTER (VNIR) MISR MOPITT CERES
IKONOS
Advanced SpaceborneThermal Emission & Reflection Radiometer - ASTER
Spatial resolution: 0.82 meter x 3.2 meters
Pre- and post-disaster images of NE-Japan Spatial resolution:15 – 30 - 90 m
Sentinel-2 Spatial resolution:
Proba-2 10-20 m
Support of the German Aerospace Center (DLR / Neustrelitz in the scope of an additional project proposal RESA Nr.621
https://centaurus.caf.dlr.de:8443/eoweb-ng/template/default/welcome/entryPage.vm
RapidEye System Specifications
Five satellites in orbit synchronous to the sun (RapidEye AG) RGB-Band-Combination
Digital Image Processing
GIS integrated evaluation
RapidEye-Mosaic with data from 2011-2013, German Aerospace Center (DLR), Neustrelitz, RESA Science Archive
5 RapidEye-Satellites in Orbit
Support of the German Aerospace Center (DLR / Neustrelitz in the scope of the project proposal RESA Nr.621: Use of RapidEye-Data for the Detection of Natural Hazard Prone Areas (Earthquake, Tsunami, Landslides, Desertification) in W-Morocco RapidEye-Mosaic with data from 2011-2013, DLR,Neustrelitz, RESA Science Archive
Report: http://resaweb.dlr.de/fileadmin/resa/documents/berichte/2012/RESA_02_2 012_0621.pdf
Satellite Data for the Detection of Tsunami prone Areas
Tsunami Events affecting the Coasts of Morocco
Bathymetric data: GEBCO
Perspective view of submarine height levels
Sources of Tsunami Waves earthquakes due to movements along fault zones volcanic activity
mass movements ( turbidity currents, submarine slope failures of sea mounts, steep canyons and cliffs)
meteo-tsunamis
cosmic impact
long-term instability of salt domes, salt pillows, etc. causing earthquakes
uplift
Tsunami Hazard Assessment The northwestern Moroccan coastline is fully exposed to the Gulf of Cadiz, where the boundary of the North African and European plates becomes convergent near the Gorringe Bank. This zone, probably one of the most dangerous seismic and tsunamigenic areas in the world, is the source of the Lisbon earthquake (M=9.0) on November, 1st, 1755AD, as well as of other historical events (216209BC, 881AD, 1731AD), that led to partial destruction of some Moroccan and south-western Iberian coastal cities. This seismogenic / tsunamigenic area continues to be active, as attested by the occurrence of the large earthquakes of 28 February 1969 (M=7.3), 26 May 1975 (M=7.9), which generated small tsunamis, and 12 February 2007 (M=6.3), strongly felt in Morocco.
F. Kaabouben, M. A. Baptista, A. Iben Brahim, A. El Mouraouah, and A. Toto: On the Moroccan tsunami catalogue. Nat. Hazards Earth Syst. Sci., 9, 1227–1236, 2009
Bathymetric maps provided by ESRI / ArcOnline
L'aperçu de niveaux de hauteur au-dessous de 40 m
Traces of Extreme Flooding-Events (Storm Surge, Tsunami Waves) on Morphometric Maps
Height Levels: Lowest Height Levels
Hillshade: Fan-shaped morphology
Minimum, Maximum, Profile Convexity Curvature: Arc-shaped walls and terraces
Aspect:
Slope:
Flat areas and slopes oriented towards the sea
• Flat abrasion planes with low slope gradients
Evaluation of Bathymetric Data (GEBCO)
Aspect
Height level
Slope degree
Curvature
Geologic map
Use of ArcGIS-tools for the extraction of causal factors from DEM data L'utilisation d'ArcGIS-instruments pour l'extraction de facteurs causaux des Données Numériques de Modell d'Élévation (DEM)
Drop-Raster
Extraction of relevant properties Extraction de propriétés pertinentes
Curvature Courbure
Slope Gradient Gradient Incliné
Drop Raster < 100.000
Slope Degree < 10°
Curvature = 0
Height Level < 10 m
Height Level < 5m
Aspect < 0
Aggregation of causal, morphometric factors influencing flooding susceptibility using the weighted overlay-tool
High susceptibility to flooding
Weighted Overlay of Causal / Preparatory Factors influencing the Flooding Susceptibility of Coastal Areas
The weighted overlay approach in ArcGIS can be used for the detection and identification of endangered lowland areas susceptible to flooding such as by flash floods. Based on ASTER Digital Elevation (DEM) data following morphometric factors as mentioned below are extracted and then aggregated in the weighted overlay tool. Factors influencing flooding susceptibility such as • relatively lowest height levels (< 10 m), • flat terrain, calculating terrain curvature (curvature values= 0, calculated in ArcMap, minimum curvature > 250 , calculated in ENVI) • slope gradients < 10° • drop raster < 100.000 • aspect < 0 (flat areas) • high flow accumulation values • watershed size.
Weighted overlay of causal factors influencing the susceptibility to flooding in the area of Essaouira
Qued Igrounzer-river mouth in the south of Essaouira
Dam flooding protection
Flooding protection measurements
Images: Theilen-Willige,2013
Susceptibility to flooding by storm surge, flash floods and tsunami waves Weighted overlay of causal factors
Weighted overlay of areas < 10 m height level, slope degree < 10°, dropraster < 100.000, minimum curvature > 250 (value calculated in ENVI software), higher flow accumulation values
Flooding susceptibility of El Jadida
Comparison of tsunami modelling
with the results of the weighted overlay
Weighted overlay result merged with the IKONOS satellite imagery of El Jadida Computed maximum inland flow depths for El-Jadida site considering the HSF+MPF tsunami scenario of magnitude Mw8.6 and Present-day-digital terrain model according to Omira et al.(2012).
Tsunami Run-up Heights
Essaouira
23 m? Tsunami run up-height as reported from the 1.November 1755earthquake (Mellas et al., 2012) and modelled by Omira et al. (2012) RapidEye-scene
Interactions between tsunami waves and coastal morphology have to be considered. The direction and angle of incoming tsunami waves play an important role when analyzing the effects of wave energy accumulation. The influence of the coastal morphology by causing local accumulation of wave energy depends among others on the angle of tsunami waves and the focussing effects of bays.
LANDSAT-Satellite Imageries used for the Inventory of Water Currents
11.09.2002
02.05.2003
The evaluations of LANDSAT imageries indicate that in the Bay of El Jadida currents might occur, amplifying wave energies. Assuming a tsunami event with waves from northern direction, there is a high probability of current development with focussing effects in this coastal segment. 10.09.1987
08.10.2003
08.10.2003
Time Series of LANDSAT Scenes of the Area of El Jadida RGB Bands 2,1,7
El Jadida
Whenever a catastrophic tsunami event happens, it must be taken into account, that the direction of the incoming waves influences the interaction with the coastal morphology to a great deal and, thus, local accumulations of wave energies. Regional meteorologic and tidal conditions have to be considered as well, as there might be synergies.
Wave Pattern and Water Currents visible on a LANDSAT 8-Image
El Jadida
28.06.2013
Figure 12
Weighted Overlay Result of the Safi Area
Potential intrusion of flood waves
Safi
Undercutting of slopes due to flood waves
Port of Safi
The absence of fan-shaped sediments at the foot-slopes and the clearly expressed escarpment seems to confirm the explanation, that these escarpments might be related to selected, lithostratigraphic units more resistant to erosion. However, it might be possible as well, that high energetic flood waves as tsunami waves undercutted the slopes and created the arc-shaped escarpments. In case of being related to flood waves these escarpments could form an indicator for the height of flood waves and the extent of flooding.
Escarpments at the slopes
Traces of flood wave erosion undercutting the slopes as visible on the IKONOS scene?
Potential slope instability in case of undercutting due to high energetic flood waves
Weighted overlay result (ASTER DEM) indicating areas susceptible to flooding due to morphometric properties
IKONOS scene Escarpments at the slopes of Safi 20 m height- contour line
Le dessin de signe de surface et les courants sous de surface d'eau près de Safi
24.04.2002
17.01.2003
19.03.2002
06.05.2011
Landsat TM
LIB
Surface wave pattern visible on LANDSAT ETM and TM imageries LANDSAT Thematic Mapper (TM)
12.10.1987
30.03.2003
20.01.2004
05.01.2011
If a tsunami arrives at high tide, or when added to the waves generated by a storm, the effects are cumulative and the inundation and destruction are greater.
Slopes oriented towards NW (red)
Safi
Safi
LANDSAT 8-Scene
Exposition of the coast – NW-oriented coastal segments oriented perpendicular towards high energetic waves will probably be more prone to flooding. Most of the energy dissipating in this coast segment is concentrated in a narrow directional spectrum.
Figure 17
Coastal segments, where the wave width and density is compressed, provide hints on areas that might be affected in case of tsunami waves by higher wave energy.
28.06.2013
Time (TTT, in minutes) and maximum wave height at the coast (MWH, in metres) modelled for a tsunami of source HSF (type 1755, Mellas et al.,2012).
Arrow-shaped and linear orientation of tsunami boulders, perpendicular to the tsunami wave fronts
Traces of former tsunami events in the south of Safi, W-Morocco Tsunami Boulders The boulders, of 4-100 tons, occur single, in imbricated sets, or form clusters and ridges. Several of the boulders were lifted and overturned. Transport distance can reach 50-100 m in this part of the coast segment.
28.06.2013
Length: 4,20 m Height: 0,80 m Width: 3,20 m
Images: Theilen-Willige,2013
Submarine Mass Movements triggering Tsunami Waves ? Traces of Compression on Slope Gradient Maps based on GEBCO Bathymetric Data The morphodynamic activity of the cliff coasts in W-Morocco is influenced by the neotectonic movements in this area due to the plate tectonic situation. The compression of the area because of the NW directed movements of the African plate and the E directed movements because of the sea-floor spreading supports especially vertical movements and, thus, coastal slope failure. The compression can be visualized on slope gradient maps based on GEBCO bathymetric data. Submarine, long- elongated , parallel, NE-SW oriented valleys and ridges as well as valley and ridges at the surface with the same orientation are obviously tracing the compression leading Slope gradient map of sea bottom topography
to folding and block-wise tectonic movements. Influence of coastal submarine topgraphy and of water streaming dynamics on the coastal slopemorphodynamic development?
El Jadida
Safi
Submarine Mass Movements triggering Tsunami Waves ?
Influence of geotectonic movements on the morphodynamic development of coastal slopes?
Slope gradient map of sea bottom topography
Traces of compression
Block gliding ?
El Jadida
Safi
Tectonic Activity Plate tectonics
Plate movements
Influence of seafloor-spreading
5 mm/y
Halokinetic movements The plate boundaries between Africa and Europe from the Atlantic to the Mediterranean, show different geodynamic contexts: – The extensional rift of Terceira in the central Atlantic. – The dextral transform fault of Azores-Gibraltar (Gloria fault) that separates the North Atlantic and Central Atlantic oceanic crust. – The intra-oceanic zone of deformation (GorringeAmpere bank) with the presence of crustal-scale thrust likely located within a larger strike-slip relay zone which can extend into the Iberian continental domain. – A wide area of continent-continent collision (AfricaEurope) at the Gibraltar arc and the Alboran Sea, probably evolving eastward into a context of active margin with incipient subduction of the crust.
GPS velocity field with respect to the Eurasia plate
Compression
Salt Tectonics in the Atlantic Margin of Morocco The Moroccan salt basin on average is ~50-150 km in width, but it stretches for at least 1000 km between the leading edge of the offshore pre-Rifean nappe in the north and the Canary Islands in the south. The significant along-strike variations in the cross-sectional and mapview distribution of the Upper Triassic to Lower Jurassic salt reflect its uneven original distribution. The seismically mapped individual salt structures such as tongues, sheets, and canopies might have originated from an autochthonous, “patchy” salt layer deposited in somewhat isolated half-grabens.
Map of Moroccan salt basin, showing major salt tectonic domains.
Subsidence, uplift and block-wise tectonic structures due to long-term salt movements http://www.searchanddiscovery.com/documents/2008/08192tari/image s/tari.pdf
Gabor Tari and Haddou Jabour (2008)
Plate tectonic movements
Fissures, Cracks and Scarps indicating Block Gliding
Agadir Canyon as visible on the Flow Accumulation Map based on GEBCO Grid Data Essaouira Seamount
Flow accumulation calculations based on GEBCO data were carried out. Thus, deep linear features in the sea bottom surface become visible. The coast-near, submarine valley pattern might be of influence on the tsunami propagation pattern and wave energy distribution. When calculating the flow accumulation based on the bathymetric data, the submarine canyons, valleys and basins can be visualized more precise.
Satellite Data for the Detection of Flash Flood prone Areas
Safi
http://www.moroccoboard.com/our-events/34news-release/4958-photos-flood-in-morocco
Prof. Dr.habil.Barbara Theilen-Willige / Technische Universität Berlin Institut für Angewandte Geowissenschaften E-mail:
[email protected]
Flash Floods in Morocco
Unusually heavy rains hit Morocco in late November 2002, giving rise to floods that killed more than 60 people. These true- and false-color images display some of the worst of the flooding just north of the city of Rabat, located on Morocco’s coast. These before and after images were acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments flying aboard NASA’s Terra and Aqua spacecrafts. Most of the casualties were due to flash flooding throughout the western half of Morocco. The water from the flash floods has drained into the now swollen riverbeds and lakebeds that appear as solid blue in the image. The floodwaters washed away loose sediment from the surrounding countryside and carried it to the Atlantic Ocean to form the sediment plumes that appear along the coast. Normally, hardly any standing water in Morocco is visible in MODIS imagery (see before images, acquired November 7, 2002). In the false color images land is green and tan, clouds are white and light blue, and water is dark blue and black. Credit: Jeff Schmaltz, MODIS Rapid Response Team, NASA/GSFC http://visibleearth.nasa.gov/view.php?id=63258
Flash floods covering the valleys
Dry season
Google Earth, 05.10.2008
Extraction of flat areas
Aspect
Extraction of factors influencing the susceptibility to flooding by flash floods, - Deriving and extracting causal or preparatory factors from Digital Elevation Data (SRTM, ASTER, TerraSAR- X- DEM) - Aggregation of Layers in ESRI-Grid-Format
Slope
Extraction of slope degrees < 10°
Drop Raster
Extraction of dropraster < 100.000
Curvature
Extraction of areas with curvatures = 0
Susceptibility Map based on the Weighted Overlay Method in ArcGIS based on ASTER DEM Data The resulting maps are divided into susceptibility classes. The susceptibility to flooding is classified by values from 0 to 6, whereby the value 6 is standing for the highest, assumed susceptibility to flooding due to the aggregation of causal / preparatory factors. Theilen-Willige (2013)
Morphometric Maps
-
Extraction of causal factors
http://resaweb.dlr.de/fileadmin/resa/documents/berichte/2012 /RESA_02_2012_0621.pdf
Safi
Susceptibility to flash floods according to the aggregation of causal, morphometric factors
RapidEye satellite scene of Safi merged with the weighted overlay results indicating in darl-blue colours the areas susceptible to flash floods due to their morphometric disposition
Perpective views of Safi
Safi
Buildings in Safi situated in areas susceptible to flash floods
Road segments intersecting areas prone to flooding in case of heavy rains causing flash floods In case of heavy rains causing flash floods it is very important to know which roads are not flooded. When planning evacuation routes, roads exposed to flooding have to be known and in case of flooding alternative routes to be arranged. In order to detect road segments susceptible to flash floods, the roadshapefiles were merged with the results of the weighted overlay of morphometric factors. Thus, those roads intersecting the areas susceptible to flooding due to their morphometric properties, can be extracted and visualized. This could be of interest for emergency planning and civil protection institutions.
Safi
Lineament analysis
Perspective view of areas susceptible to flash floods Linear and parallel arrangements of the susceptible areas are visible.
Flash flood areas in Casablanca
Weighted overlay of causal factors enhancing the susceptibility to be prone to flooding
Weighted overlay
Drainage pattern
Traces of Storm Surge
28.06.2013 RapidEye Scene
Currents at the coast of Agadir
09.02.1988
Agadir
12.04.2005 (false colour composites of the LANDSAT Bands: 2, 1 and 7)
Monitoring of Oulja-Areas with Remote Sensing and GIS-Tools of the Atlantic Coasts of W-Morocco
Image: Halima AIT MALEK
Evaluation of LANDSAT Time Series with Different Acquisition Times for Change Detection
05.09.1973
16.08.1984
02.07.1985
1986
11.09.2002
08.10.2003
24.06.2011
26.04.2013
LANDSAT 8 - latest satellite imageries from the USGS EarthExplorer
Detection of surface water and wetlands based on RapidEye- satellite data using the waterindex NDWI
RGB Bands 3,2,1- image, 10.12.2012
NDWI, Bands 2 and 5, water surfaces are presented in white. Oualidia
Images: Theilen-Willige, 2013
RapidEye-scenes of the Oualidia- area
Water surfaces appear in white on the NDWI-image
Environmental Influences
RapidEye and Google Earth-scenes
N Perspective 3D views of the coast of Safi using RapidEye satellite data
N
S
W
N
Safi
Perspective 3D view of the coast of Safi using RapidEye satellite data
Conclusions
The nearly world-wide available SRTM and ASTER-DEM data and high resolution satellite imageries support a standardized, low- cost approach for the detection of some of the causal factors of local conditions influencing flooding susceptibility and damage.
Whatever might be the source of extreme flooding events, the lowest and flattest coastal areas and river mouths will be prone first. Therefore maps are recommended showing coastal areas susceptible to flooding due to their morphometric disposition. A flooding hazard map of coastal areas, that predicts the probable locations of possible future inundation is required which takes into consideration as well the potential morphodynamic consequences of these events at the coasts such as, abrasion, sedimentation and mass movements. By undercutting slopes.
The long-term evaluation of availabe satellite imageries combined with additional geodata might contribute to a better understandig of the complex wave pattern in a specific tsunami situation and the different influences on currents (wind, temperature, etc.). 77
Thank you for your attention
http://resaweb.dlr.de/fileadmin/resa/documents/berichte/2012/RESA_02_2012_0621.pdf
