Analysis of the recent deformation in Tunis by interferometry radar SAR

Les phénomènes de déformation du sol d‘origines naturelles (tectoniques et gravitaires...) ou anthropiques (surexploitation des nappes phréatiques, remblaiements...) peuvent avoir des retombées néfastes sur l'environnement et sur la vie humaine. Une bonne compréhension du mécanisme de la déformation est essentielle pour atténuer voire éliminer les risques sur les infrastructures et les environnements naturels. Dans cette étude, on se propose d‘appliquer la méthode interférométrique pour étudier la mobilité sur le grand Tunis qui est une zone urbaine et suburbaine et qui correspond au principal centre socio-économique de Tunisie. Tout d'abord, nous avons effectué des analyses sismotectoniques dans la zone d‘étude pour mieux comprendre les contextes sismique et structurale de la partie NE de la Tunisie tout en se basant sur différentes interprétations effectuées à partir des mécanismes au foyer et de la cartographie des épicentres réalisés dans cette zone. Cette analyse a permis de déduire l‘existence d‘un régime compressif NW-SE qui concorde bien avec le régime déjà existant à l‘échelle régionale. Cette cartographie a permis aussi la détection des différentes zones marquées par une activité sismique relativement importante avec une magnitude modérée et qui coïncident bien avec les accidents majeurs qui affectent la zone d‘étude. Par la suite, nous avons mené une analyse géomorphométrique du secteur d‘étude qui a permis de mettre en évidence différentes structures tectoniques existantes et de bien distinguer les différentes unités morphologiques et morphostructurales. Pour mieux assimiler le contexte morphodynamique de la zone d‘étude, nous avons choisi la méthode interférométrique des sous-ensembles à faibles lignes de base spatiales et temporelle (SBAS) qui est développée par Berardino et al. (2002). En effet, l‘application de l‘interférométrie radar différentiel sur la partie NE de la Tunisie a permis d‘identifier les zones à risques de subsidence naturelles et l'analyse des déformations de la surface topographique, associées aux phénomènes anthropiques. L‘analyse interférométrique des images radars à ouverture synthétique SBAS a démontré sa capacité de surveiller les déformations de la surface topographique et notamment les phénomènes de subsidence "à distance" avec une densité élevée de mesures au sol sur une large zone dans plusieurs travaux à travers le monde. Les analyses effectuées sur les données radar Envisat (2003-2007) en orbite descendante et Sentinel-1B (2016-2018) en orbite ascendante, nous ont permis d‘obtenir des cartes de déformation du sol, associées à des séries temporelles de la vitesse de déplacement de la zone d‘étude. Durant les deux périodes d‘analyses, nos résultats ont révélé et confirmé l‘existence de phénomènes de tassement différentiel dans la région de Tunis et de la plaine alluviale de Mornag. Le premier cas est très probablement expliqué par la nature du remblaiement et du sol hautement compressible dans la région de Tunis. Le deuxième cas consiste en un faible affaissement très probablement lié à une exploitation intensive du système aquifère de Mornag (pompage)Soil deformation phenomena of natural (tectonic) or anthropic origins (over exploitation of groundwater, embankment) can have adverse effects on the environment and on human life. A good understanding of the mechanism of deformation is essential to mitigate or eliminate risks to infrastructure and natural environments. In this study, it is proposed to apply the interferometric method to study the mobility of an urban and suburban area of Tunis City, which is the main socio-economic center of Tunisia.Seismotectonic analyzes were carried out in the study area to better understand the seismic and structural context of the North East part of Tunisia while being based on the different interpretations made from focal mechanisms and mapping epicentres in this area. This analysis made it possible to deduce the existence of an NW-SE compressive regime that fits well with the existing regime at the regional level. This mapping also allowed the detection of the different zones marked by a relatively large seismic activity with a moderate magnitude and which coincide well with the major accidents that are at the level of the study area. Subsequently, a geomorphological analysis approach of the study area was carried out, which made it possible to highlight the different existing tectonic structures and to distinguish the different morphological units. It has been shown that geomorphological analysis has limitation to interpret the morphodynamic context of the study area and therefore the interferometric technique has proven to be an effective methodology for detecting and monitoring soil displacements with millimeter precision and also improving our understanding of current deformations. Indeed, the application of differential SAR interferometry made it possible to nether identify areas with natural subsidence risks or analyze the deformations of the topographic surface associated with anthropic phenomena. To better assimilate the morphodynamic context of the study area, the interferometric method of Small Baseline Subset (SBAS) developed by Berardino et al. (2002) has been chosen. The analysis of Envisat ASAR (2003-2007, descending satellite orbit) and Sentinel-1B (2016-2018, ascending satellite orbit) SAR data allowed us to obtain soil deformation maps associated with time series of velocity of the study area. These analyzes showed the existence of a differential settlement phenomenon in the region of Tunis and the Mornag plain by quantifying it quite accurately. Therefore, by combining SBAS results with geological, hydrogeological and geotechnical information, we have been able to explore some of the links between soil subsidence and its main control factors, in particular:- a differential settlement detected around the Lake of Tunis region, which is probably due to the nature of highly compressible alluvial sediments with bedrock depths sometimes exceeding 65m;- a subsidence of the Mornag plain, whose overexploitation of groundwater and the compressibility of alluvium were the driving forces of these deformation

Analyse de la déformation récente dans le Grand Tunis par interférométrie radar SAR (v2)

Les phénomènes de déformation du sol d’origines naturelles (tectoniques et gravitaires...) ou anthropiques (surexploitation des nappes phréatiques, remblaiements...) peuvent avoir des retombées néfastes sur l'environnement et sur la vie humaine. Une bonne compréhension du mécanisme de la déformation est essentielle pour atténuer, voire éliminer les risques sur les infrastructures et les environnements naturels. Dans cette étude, on se propose d’appliquer la méthode interférométrique pour étudier la mobilité du sol du Grand Tunis qui est une zone urbaine à suburbaine qui correspond au principal centre socio - économique de Tunisie ainsi que sur la plaine de Mornag. Tout d'abord, nous avons effectué des analyses sismotectoniques dans la zone d’étude pour mieux comprendre les contextes sismique et structurale de la partie NE de la Tunisie tout en se basant sur différentes interprétations effectuées à partir des mécanismes au foyer et de la cartographie des épicentres réalisés dans cette zone. Cette analyse a permis de déduire l’existence d’un régime compressif NW - SE qui concorde bien avec le régime déjà existant à l’échelle régionale. Cette cartographie a permis aussi la détection des différentes zones marquées par une activité sismique relativement importante avec une magnitude modérée et qui coïncident bien avec les accidents majeurs qui affectent la zone d’étude. Par la suite, nous avons mené une analyse géomorphométrique du secteur d’étude qui a permis de mettre en évidence différentes structures tectoniques existantes et de bien distingué les différentes unités morphologiques et morphostructurales. Pour mieux assimiler le contexte morphodynamique de la zone d’étude, nous avons choisi la méthode interférométrique des sous - ensembles à faibles lignes de base spatiales et temporelle (SBAS) qui est développée par Berardino et al. (2002). En effet, l’application de l’interférométrie radar différentiel sur la partie NE de la Tunisie a permis d’identifier les zones à risques naturelles liées à la subsidence et l'analyse des déformations de la surface du sol, associées aux phénomènes anthropiques. ` 5 L’analyse interférométrique des images radars à ouverture synthétique SBAS a démontré sa capacité de surveiller les déformations de la surface du sol et notamment les phénomènes de subsidence "à distance" avec une densité élevée de mesures au sol sur une large zone dans plusieurs travaux à travers le monde. Les analyses effectuées sur les données radar Envisat (2003 - 2007) en orbite descendante et Sentinel - 1B (2016 - 2018) en orbite ascendante, nous ont permis d’obtenir des cartes de déformation du sol, associées à des séries temporelles de la vitesse de déplacement de la zone d’étude. Durant les deux périodes d’analyses, nos résultats ont révélé et confirmé l’existence de phénomènes de tassement différentiel dans la région de Tunis et de la plaine alluviale de Mornag. Le premier cas est très probablement expliqué par la nature du remblaiement et du sol hautement compressible dans la région de Tunis. Le deuxième cas consiste en un faible affaissement très probablement lié à une exploitation intensive du système aquifère de Mornag (pompage).Soil deformation phenomena of natural (tectonic) or anthropic origins (over exploitation of groundwater, embankment) can have adverse effects on the environment and on human life. A good understanding of the mechanism of deformation is essential to mitigate or eliminate risks to infrastructure and natural environments. In this study, it is proposed to apply the interferometric method to study the mobility of an urban and suburban area of Tunis City, which is the main socio-economic center of Tunisia.Seismotectonic analyzes were carried out in the study area to better understand the seismic and structural context of the North East part of Tunisia while being based on the different interpretations made from focal mechanisms and mapping epicentres in this area. This analysis made it possible to deduce the existence of an NW-SE compressive regime that fits well with the existing regime at the regional level. This mapping also allowed the detection of the different zones marked by a relatively large seismic activity with a moderate magnitude and which coincide well with the major accidents that are at the level of the study area. Subsequently, a geomorphological analysis approach of the study area was carried out, which made it possible to highlight the different existing tectonic structures and to distinguish the different morphological units. It has been shown that geomorphological analysis has limitation to interpret the morphodynamic context of the study area and therefore the interferometric technique has proven to be an effective methodology for detecting and monitoring soil displacements with millimeter precision and also improving our understanding of current deformations. Indeed, the application of differential SAR interferometry made it possible to nether identify areas with natural subsidence risks or analyze the deformations of the topographic surface associated with anthropic phenomena. To better assimilate the morphodynamic context of the study area, the interferometric method of Small Baseline Subset (SBAS) developed by Berardino et al. (2002) has been chosen. The analysis of Envisat ASAR (2003-2007, descending satellite orbit) and Sentinel-1B (2016-2018, ascending satellite orbit) SAR data allowed us to obtain soil deformation maps associated with time series of velocity of the study area. These analyzes showed the existence of a differential settlement phenomenon in the region of Tunis and the Mornag plain by quantifying it quite accurately. Therefore, by combining SBAS results with geological, hydrogeological and geotechnical information, we have been able to explore some of the links between soil subsidence and its main control factors, in particular:- a differential settlement detected around the Lake of Tunis region, which is probably due to the nature of highly compressible alluvial sediments with bedrock depths sometimes exceeding 65m;- a subsidence of the Mornag plain, whose overexploitation of groundwater and the compressibility of alluvium were the driving forces of these deformations

DEM Study on Hydrological Response in Makkah City, Saudi Arabia

The changes in catchments can be analyzed through the generation of DEM, which is important as input data in hydrologic modeling. This study aims to analyze the effect of anthropogenic activities on hydrological studies based on DEM comparison and GIUH hydrographs. The four DEM datasets (SRTM, ALOS, Copernicus, Sentinel-1) were compared to the topographic map of Makkah City and GPS data in order to assess the quality of the DEM elevation. The GIS Arc Hydro toolbox was used to extract morphometric and Horton–Strahler ratio characteristics to generate a GIUH hydrograph of the catchments of Wadi Nouman and Wadi Ibrahim inside Makkah City. Based on the DEM comparison, Copernicus and SRTM have the highest accuracy, with R2 = 0.9788 and 0.9765, and the lowest RMSE, 3.89 m and 4.23 m, respectively. ALOS and Sentinel-1 have the lowest R2, 0.9687 and 0.9028, and the highest RMSE, 4.27 m and 6.31 m, respectively. GIUH Copernicus DEM on Wadi Nouman has a higher qp  and lower tp (0.21 1/h and 2.66 h) than SRTM (0.20 1/h and 2.75 h), respectively. On Wadi Ibrahim, the SRTM has a greater qp and lower tp  than Copernicus due to the wadi having two shapes. Based on the anthropogenic effect, the stream network in the mountain area is quite similar for SRTM and Copernicus due to the dominant influence of the mountainous relief and relatively inconsequential influence of anthropogenic activities and DEM noise. In the urban area, the variation of the stream network is high due to differing DEM noise and significant anthropogenic activities such as urban redevelopment. The Copernicus DEM has the best performance of the others, with high accuracy, less RMSE, and stream flow direction following the recent condition

Monitoring of mangrove forests vegetation based on optical versus microwave data: A case study western coast of Saudi Arabia

Normalized difference vegetation index (NDVI) is one of the parameters of vegetation that can be studied by remote sensing of land surface with Sentinel-2 (S-2) satellite image. The NDVI is a nondimensional index that depicts the difference in plant cover reflectivity between visible and near-infrared light and can be used to measure the density of green on a piece of land. On the other hand, the dual-pol radar vegetation index (DpRVI) is one of the indices studied using multispectral synthetic aperture radar (SAR) images. Researchers have identified that SAR images are highly sensitive to identify the buildup of biomass from leaf vegetative growth to the flowering stage. Vegetation biophysical characteristics such as the leaf area index (LAI), vegetation water content, and biomass are frequently used as essential system parameters in remote sensing data assimilation for agricultural production models. In the current study, we have used LAI as a system parameter. The findings of the study revealed that the optical data (NDVI) showed a high correlation (up to 0.712) with LAI and a low root-mean-square error (0.0296) compared to microwave data with 0.4523 root-mean-square error. The NDVI, LAI, and DpRVI mean values all decreased between 2019 and 2020. While the DpRVI continued to decline between 2020 and 2021, the NDVI and LAI saw an increase over the same period, which was likely caused by an increase in the study area’s average annual rainfall and the cautious stance of the Red Global (RSG) project on sustainability

Design of a New Phthalocyanine-Based Ion-Imprinted Polymer for Selective Lithium Recovery from Desalination Plant Reverse Osmosis Waste

In this study, a novel technique is introduced that involves the combination of an ion-imprinted polymer and solid-phase extraction to selectively adsorb lithium ions from reverse osmosis brine. In the process of synthesizing ion-imprinted polymers, phthalocyanine acrylate acted as the functional monomer responsible for lithium chelation. The structural and morphological characteristics of the molecularly imprinted polymers and non-imprinted polymers were assessed using Fourier transform infrared spectroscopy and scanning electron microscopy. The adsorption data for Li on an ion-imprinted polymer showed an excellent fit to the Langmuir isotherm, with a maximum adsorption capacity (Qm) of 3.2 mg·g−1. Comprehensive chemical analyses revealed a significant Li concentration with a higher value of 45.36 mg/L. Through the implementation of a central composite design approach, the adsorption and desorption procedures were systematically optimized by varying the pH, temperature, sorbent mass, and elution volume. This systematic approach allowed the identification of the most efficient operating conditions for extracting lithium from seawater reverse osmosis brine using ion-imprinted polymer–solid-phase extraction. The optimum operating conditions for the highest efficiency of adsorbing Li+ were determined to be a pH of 8.49 and a temperature of 45.5 °C. The efficiency of ion-imprinted polymer regeneration was evaluated through a cycle of the adsorption–desorption process, which resulted in Li recoveries of up to 80%. The recovery of Li from the spiked brine sample obtained from the desalination plant reverse osmosis waste through the ion-imprinted polymer ranged from 62.8% to 71.53%

Flash flood risk assessment in urban arid environment:case study of Taibah and Islamic universities’ campuses, Medina, Kingdom of Saudi Arabia

Abstract Flooding impacts can be reduced through application of suitable hydrological and hydraulic tools to define flood zones in a specific area. This article proposes a risk matrix technique which is applied on a case study of Taibah and Islamic universities catchment in Medina, Kingdom of Saudi Arabia (KSA). The analysis is based on integration of the hydrologic model hydraulic models to delineate the flood inundation zones. A flood risk matrix is developed based on the flood occurrence probability and the associated inundation depth. The risk matrix criterion is classified according to the degree of risks as high, moderate and low. The case study has indicted low to moderate risk for flood frequencies of 5 years return periods and moderate to high risk may exist for flood with rerun period of 50 and 100 years. The results are projected on a two-dimensional satellite images that shows the geographical locations exposed to flooding. A quantitative summary of the results have been presented graphically to estimate the magnitude of the inundation areas that can assess the degree of damage and its economic aspects. The developed flood risk matrix tool is a quantitative tool to assess the damage which is crucial for decision makers

The impact of rainfall distribution patterns on hydrological and hydraulic response in arid regions:case study Medina, Saudi Arabia

Abstract Rainfall distribution patterns (RDPs) are crucial for hydrologic design. Hydrologic modeling is based on Soil Conservation Services (SCS) type RDPs (SCS type I, IA, II, and III). SCS type II method is widely used by hydrologists in arid regions. These RDPs were designed for the USA and similar temperate regions. There is no scientific justification for using SCS type II method in arid regions. The consequences of using SCS type II have impacts on the hydrologic and hydraulic modeling studies. The current paper investigates the validity of the SCS type II and in arid regions. New temporal RDPs were applied and compared with SCS type II RDPs. The produced peak discharges, volumes, maximum inundation depths, top widths, and velocities from both approaches were analyzed. An application is made on the protection channel in Taibah and Islamic Universities campuses in Medina, Saudi Arabia. A methodology was followed which included frequency analysis, catchment modeling, hydrological modeling, and hydraulic modeling. Results indicated that there are considerable consequences on infrastructural design, and hydrologic and hydraulic parameters if inappropriate RDPs are used. The investigation confirmed that the SCS type RDPs do not reflect the actual flood features in arid regions