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International Institute for Geo-Information Science and Earth Observation (ITC) 2012

Assessment of drought hazard : A case study in Sehoul area, Morocco.

Otgonjargal Natsagdorj

Titre : Assessment of drought hazard : A case study in Sehoul area, Morocco.

Auteur : Otgonjargal Natsagdorj

Etablissement de soutenance : University of Twente International Institute for Geo-Information Science and Earth Observation (ITC)

Grade : Master of Science in Geo-Information Science and Earth Observation 2012

Résumé partiel
This research deals with the assessment of drought hazard over Sehoul area of Morocco. Morocco is highly susceptible to recurrent droughts with long periods (one to six years) due to arid climate and the strengthening effect of the Azores anticyclone . The focus of this research is on increasing the understanding and applying the basic concepts, drought hazard and hazard assessment. Drought is a natural hazard originating from a deficiency of precipitation that results in a water shortage for some activities or groups. Drought hazard assessment is one of the stages of drought risk assessment. Thus it is essential for taking mitigation measures against adverse drought effects and for planning and managing water related policy. The important aspects of drought hazard assessment such as temporal and spatial occurrence as well as vegetation response to precipitation were included for this research. Meteorological droughts where rainfall is the main parameter of interest was studied based on long term rainfall data (1950- 2010) and vegetative drought was examined using SPOT NDVI data (1km) between the periods of 1998- 2010 under the consideration that precipitation is a primary factor of vegetative drought . In addition , Aster image on 21 Oct 2011 was used to generate land cover map . Rainfall analysis was carried out in order to investigate the amount and timing of rainfall on vegetation. Moreover, t rend analysis of extreme rainfall was conducted. The Standardized Precipitation Index (SPI) was employed to identify historical meteorological droughts and perform drought magnitude frequency analysis, applying the Joint Probability Density Function (PDF). Drought Severity Index (DSI) was used to assess spatial occurrence of vegetative drought. To examine vegetation response to variability in precipitation, time lags and vegetation phenological approach were applied . Based on the results obtained, the years of vegetative droughts were constructed during the period 1951- 1997 in which SPOT NDVI data is not available and compared to the information on observed droughts found from literature . Finally, RESTREND method was employed to discriminate climate and human- induced vegetation decrease .

Version intégrale (ITC)

Page publiée le 5 février 2018