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2 Ecological Engineering & Environmental Technology

2 2023

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Remote Sensing at the Service of Wetlands Mapping: A Case of the Lower Loukkos Complex (North-West Morocco)

100%

Fathi B. , Tribak A. A. , Wahbi M. , Maâtouk M. , Sebbah B.

tom Vol. 24, iss. 8

225--239

Despite their highly recognized ecological values and ecosystem services, approved by the scientific community, wetlands are in perpetual degradation and their global spatial extension in significant regression. The conservation and sustainability of such ecosystems begins with their monitoring and delimitation. This study aims to develop an approach using open access remote sensing data to make this delineation. Applied to the coastal wetland complex of the lower Loukkos in the Mediterranean area, the methodology followed a two-step process. Firstly, it predicted the spaces favourable for water accumulation conditions, and secondly, it identified the presence of water and its response on the soil and vegetation. The approach was based on a theoretical modelling adopting the potential, existing, efficient wetland (PEEW) approach. The recordings from Sentinel sensors served as the basis for calculating indices Beven-Kirkby Index (BKI), Buffer zone Index (BZI), Normalized Difference Moisture Index (NDMI), Normalized Difference Vegetation Index (NDVI) and Modified Normalized water difference index (MNDWI) to pre-locate and model potential wetland areas (PW). Photo Interpretation was used to map the existing wetland areas (EW). The estimated area of wetlands in the lower Loukkos region is 379 km2 for potential areas identified from topographic data and the hydrographic network, 120 km2 for areas dominated by wetlands detected by remote sensing of water bodies , vegetation and soil moisture, and 33 km2 for natural wetlands identified by photo-interpretation. As a result, the area of current wetlands is only about 9.5% of their theoretical past extent. The validity of this method was confirmed through a comparison of the results with field investigations and hydromorphic traits in soil surveys, as well as external soil mapping data, showing an 84% concordance.

Towards Time Series Sensor Data to Accurately Map Flood Hazard and Assess Damages under Climate Change Using Google Earth Engine Cloud Platform and GIS – Case of the Cities of Tetouan and Casablanca (Morocco)

86%

El Yacoubi Y. , Wahbi M. , Maatouk M. , El Kharki O. , Boulaassal H. , Alaoui O. Y.

tom Vol. 24, iss. 5

238--253

Climate change poses a major challenge in terms of urban planning management for the sake of a sustainable future. It is affecting the hydrological cycle around the world, leading to extreme weather conditions. Floods rank as the most frequent and widespread disaster in the world, they adversely affect inhabitants in terms of property damage and threat to human safety (and lives, in the worst cases). Uncontrolled urban sprawl also exacerbates floods by expanding impervious surfaces and affecting flow paths. Other factors that trigger flooding (apart from the rainfall intensity) are human involvement in the main waterways, thereby significantly impacting the hydraulic flow characteristics, structural engineering breakdowns, compounded by potential deforestation. For the purpose of monitoring the aftermath of floods experienced by the cities of Casablanca and Tetouan (Morocco) respectively in January and March 2021 and estimating their damages, optical and radar satellite images derived from the Google Earth Engine (GEE) cloud platform were used along with the Geographic Information System (GIS). In this study, a novel technique for extracting flooded areas from high-resolution Synthetic Aperture Radar (SAR) time series images has been developed. A comparison was carried out subsequently between the time-series approach and other traditional approaches including radiometric thresholding method, spectral indices namely Normalized Difference Water Index (NDWI) and Modified Normalized Difference Water Index (MNDWI) as well as Flood Water Index (FWI). Based on the above approach, the water levels were estimated and the damages were assessed and mapped, notably the number of people exposed to flood hazard and the amount of built-up areas and cropland affected. The results demonstrated that Casablanca city has witnessed a higher flood level than Tetouan city, putting a large number of people at risk and affecting a significant area of land use. The findings can also provide local authorities with a comprehensive view of flooding and enable them to make decisions on preparedness, mitigation, and adaptation to flood-related disasters.