Mapping karstic geohazards in the Safi region

Mapping karstic geohazards in the Safi region, Morocco,
by the use of Landsat, Ikonos and RapidEye images
Charif A.1, Aït Malek H.1 , El Bchari F.1, Theilen-Willige B.2, Chaibi M.1, Löwner R.2, Ridaoui M.1, Ayt Ougougdal M.1, Nakhcha C.1
1
2
Cadi Ayyad University, Polydisciplinary Faculty, BP : 4162 - Sidi Bouzid – Safi, Morocco
TU Berlin, Institute of Applied Geosciences, D- 13355 Berlin, Ackerstraße 76, Germany
Geographic Lacation
Problematic
The study area is part of the arid to semi-arid
Moroccan coastal plateau (fig. 1).
In the region of Safi, carbonate rocks are
significantly influenced by the phenomena of
dissolution. Here, cavities and other karst
phenomena are the result of the effect of
aggressive water on Jurassic-Cretaceous
limestones and Plioquaternairy biodetritic
limestones, and in particular of the circulation
of groundwater.
These karst processes are responsible for both
underground (caves) and visible surface
phenomena (dolines, loss points, collapses ...).
The presence of karst phenomena and their
continual evolution is a serious problem of soil
stability and may require caution in
urbanization.
1
2
3
4
(8°30W, 32°30N)
Location of the study
area
(9°00W,
32°00N)
Geology
Karst formations in the study area:
1: Dolines, 2: Cave in the south of Safi, 3: localisation of the
cave of Gouraani, 4: Cave of Gouraani to the north of Safi
Example of Karstic phenomena
The geological setting of the Safi region presents
outcrops from Jurassic to Quaternary time.
Cave of Gouraani (North of Safi)
Stalactites and
Stalagmites
Results
Typical karst landscapes near Safi related to
Cretaceous rocks can be identified on satellite
imageries. The morphometric analysis of digital
elevation data helps to visualize the smallscaled variations on the surface, characterized
by very slight changes of altitudes.
Discussion & Conclusion
Interior view
of the cave
Fig 2.
Stratigraphic setting of the study area
Fig 4.
Morphometric analysis
Evaluations of satellite data for
the detection of karst features
Fig 3.
The developed method allows detection of
karst structures (e.g., dolines, ..) from Landsat,
Ikonos and RapidEye satellite data, taking into
account the geology, tectonic and pedology of
the region.
However,
the
realization
of
colored
compositions able to provide accurate and
relevant
information
can
be
made
independently of a deep knowledge of the
area.
In this context we evaluated the contribution
of remote sensing in analyzing the
environmental settings of the Safi region,
where many indicators of karst phenomena are
preserved. The results are very promising and
the level of karstification could be classified in
different levels of intensity.
Thus, areas prone to important problems
coming up with karstification could be
identified and they are in the focus of future
detailed investigation.
Detection of Karst structures through satellite data: Dolines oriented N170-195, N040-070, N080-115, which are mainly “Mesetian” & “Atlasic” tectonic directions of Atlantic Morocco
Realized in the in the framework of the project: GeRiSa - Environmental risk management in the region of Safi, Morocco
Project Leader: Prof. Dr. Wilhelm Dominik, Institute of Applied Geosciences, TU Berlin
Project Sponsors:

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