Remote Sensing and GIS Contribution to the Detection of potential natural hazards at the Coast of Safi, Morocco

Abstract:

The geomorphologic and topographic features and characteristics of the Atlantic coast of Morocco are similar to areas hit by recent catastrophic tsunamis as Sumatra and Japan, where historic records of floods and tsunami events are available and reliable.
Around the sea side and near-shore zone of Morocco there is a potential for generation of tsunamis and storm surge. Parts of the coastline have suffered from disastrous marine waves in history. Historical earthquakes and associated tsunamis are identified from verified catalogues (EMSC, ISC, NOAA). The tsunami waves flooded low lands in many segments of the coast. In addition to historical and geologic information, or distribution of fault zones and other probable tsunamigenic sea bottom structures, there are numerous source areas which may be considered responsible for severe tsunami events.

Responding to these potential hazards, the Safi region is taken as a showcase environment in order to investigate flooding susceptibility and landslide mapping for coastal areas in Morocco. These research activities are accompanied by the development of appropriate data infrastructures to provide the required data and information for land and risk management.

The Safi region is located on the Atlantic coast between the lagoon of Oualidia and the Tensift river basin, and belongs to the Coastal Meseta, forming an erosional platform covered by accumulations of various Cenozoic sediments. Transgressive and regressive fluctuations during the Quaternary generated a rich variety of geomorphological units (flooded erosional platforms, depressions, plateaus, cliffs, consolidated dunes, wadis, estuaries, lagoons, gutters, etc.), suitable for detailed studies of different potential hazard models.
The study area illustrates its importance for the national economy by intensive social-economical activities (such as the treatment and shipping of a huge amount of phosphates coming from the interior of the country).
Indeed, this region shows many environmental problems associated with flooding, landslides and ground instabilities in addition with surface subsidence damages related among others to karstification structures.

In this sense, this multidisciplinary project focuses on a synthesis of various works, approaches and collaborations in-progress, previous completed projects and already existing data. It combines and uses actual and previous efforts by adding new researches focusing on remote sensing, and new techniques in Geographic Information Systems (GIS) and Geoinformatics.

This study is considering flooding susceptibility mapping for coastal areas in Morocco. A flooding risk map and a potential tsunami hazard map of affected coastal areas that deals with the susceptible location of future floods and tsunami inundation and the induced secondary effects such as abrasion and landslides is required.
The areas of potential risks are delineated by an integration of remote sensing data, geologic, seismotectonic, bathymetric and topographic data and data of historic tsunami or landslide events. ASTER, RapidEye, LANDSAT ETM and SRTM data are used for generating an image based GIS and combined with different geodata and other thematic maps.

In order to integrate all available data, a local information system based on an adapted data infrastructure will be realized at the campus of the University in Safi, Morocco, rebinding the former pilot project SaDIN (Sahel-Doukkala Scientific Information Network). Hereafter, various web services will be developed in order to create a WebGIS, accessible for all concerned.
This local and regional data infrastructure will be the first step towards future concepts using observation and monitoring systems. Dynamic data and information available in real time, at the right place and in adequate formats enables appropriate responses to detrimental alterations e.g., landslides and Tsunamis.

The use of international standards according to the OGC and capacity building within the local staff are relevant growth factors. Free and Open Source Software (FOSS) could help to reduce the costs, achieve independence from software products and enhance the feasibility of the project.

This work will be the starting point for a risk assessment as well as a warning system for the population of the Safi region. This “bottom up” approach could stimulate similar projects in other regions or countries and the transfer of technology and know-how.

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