scholarly journals Brief communication: Radar images for monitoring informal urban settlements in vulnerable zones in Lima, Peru

2021 ◽  
Author(s):  
Luis Moya ◽  
Fernando Garcia ◽  
Carlos Gonzales ◽  
Miguel Diaz ◽  
Carlos Zavala ◽  
...  
Keyword(s):  
Natural Hazards ◽  
Soil Conditions ◽  
Social Phenomenon ◽  
Sar Images ◽  
Informal Housing ◽  
Radar Images ◽  
Housing Subsidies ◽  
Urban Settlements ◽  
Informal Urban Settlements ◽  
Vulnerable Zones

Abstract. Lima city, Peru's capital, has about 9.6 million inhabitants and keeps attracting more residents searching for a better life. Many citizens, without access to housing subsidies, live in informal housing and shack settlements. A typical social phenomenon in Lima is the sudden illegal occupation of areas for urban settlements. When such areas are unsafe against natural hazards, it is important to relocate such a population to avoid significant future losses. In this communication, we present an application of Sentinel-1 SAR images to map the extension of a recent occupation of an area with unfavorable soil conditions against earthquakes.

scholarly journals Brief communication: Radar images for monitoring informal urban settlements in vulnerable zones in Lima, Peru

2022 ◽  
Vol 22 (1) ◽  
pp. 65-70
Author(s):  
Luis Moya ◽  
Fernando Garcia ◽  
Carlos Gonzales ◽  
Miguel Diaz ◽  
Carlos Zavala ◽  
...  
Keyword(s):  
Synthetic Aperture ◽  
Soil Conditions ◽  
Social Phenomenon ◽  
Sar Images ◽  
Informal Housing ◽  
Radar Images ◽  
Housing Subsidies ◽  
Urban Settlements ◽  
Informal Urban Settlements ◽  
Vulnerable Zones

Abstract. Lima, Peru's capital, has about 9.6 million inhabitants and keeps attracting more residents searching for a better life. Many citizens, without access to housing subsidies, live in informal housing and shack settlements. A typical social phenomenon in Lima is the sudden illegal occupation of areas for urban settlements. When such areas are unsafe against natural hazards, it is important to relocate such a population to avoid significant future losses. In this communication, we present an application of Sentinel-1 synthetic aperture radar (SAR) images to map the extension of a recent occupation of an area with unfavorable soil conditions against earthquakes.

Potential impacts of slum urbanisation on channel bank storage in the Bang Pakong River, Thailand

2012 ◽  
Vol 7 (4) ◽  
Author(s):  
K. Harriden
Keyword(s):  
Water Quality ◽  
Balance Equations ◽  
Physical Processes ◽  
Social Phenomena ◽  
Urban Settlements ◽  
Recharge Rates ◽  
Water Quality Deterioration ◽  
Informal Urban Settlements ◽  
Storage Processes

Generally regarded as social phenomena, this paper regards slum urbanisation as an environmental actor. Specifically, how slum developments modify hydrogeomorphological processes motivates this research. Using the Bang Pakong River, eastern Thailand, as a case study, a literature review was conducted. The literature reviewed indicated changes in physical processes such as channel bank stability, water quality, flow regimes and the hydrological balance equations can occur with slum development. Given the importance of channel banks as the physical basis of many slum sites, this paper focuses on the possible changes to channel bank storage in the Bang Pakong River following slum urbanisation. The research highlights possible changes to channel bank storage processes, notably decreased storage recharge rates; increased anthropogenic extraction; and probable water quality deterioration. Deeper scientific understanding of how river processes are affected by specific forms of urban development can contribute to better management of both informal urban settlements and rivers.

The Quest for Water, Rights and Freedoms: Informal Urban Settlements in India

2018 ◽  
Vol 42 (6) ◽  
pp. 1080-1095
Author(s):  
Francesco M. Gimelli ◽  
Briony C. Rogers ◽  
Joannette J. Bos
Keyword(s):  
Water Rights ◽  
Urban Settlements ◽  
Informal Urban Settlements

scholarly journals A Proposed Approach to Determine the Edges in SAR images

2020 ◽  
pp. 185-192
Author(s):  
Rabab Farhan Abbas
Keyword(s):  
Edge Detection ◽  
Electromagnetic Waves ◽  
Operator Method ◽  
Bézier Curve ◽  
Bezier Curve ◽  
Edge Image ◽  
Sar Images ◽  
Wavelet Method ◽  
Radar Images ◽  
Sobel Operator

Radar is the most eminent device in the prolonged scattering era The mechanisms involve using electromagnetic waves to take Synthetic Aperture Radar (SAR) images for long reaching. The process of setting edges is one of the important processes used in many fields, including radar images, which assists in showing objects such as mobile vehicles, ships, aircraft, and meteorological and terrain forms. In order to accurately identify these objects, their edges must be detected. Many old-style methods are used to isolate the edges but they do not give good results in the  determination process. Conservative methods use an operator to detect the edges, such as the Sobel operator which is used to perform edge detection where the edge does not appear well.      The proposed method which combines Ridgelet transform, Bezier curve and Sobel operator is used to detect edges very efficiently. Ridghelet transform resolves the harms in the wavelet transform and it can well detect the edges in images. Bezier curve can profit gradual variation of the data and their mutability. Hence, the efficiency of the edged image is improved and, when used with Sobel operator, the quality of the edge image become very good. The data show that the advocated method has superior fallouts over the Sobel edge detection and the wavelet method in both subjective and impartial experiments. While the Peak Signal to Noise Ratio(PSNR) values were equal to 9.3812, 9.8918, 9.6521 and 9.0743using the Sobel operator method and to10.2564, 10.7927, 10.5612and 10.8633 using the wavelet method, they were increased in the proposed method to 12.6542, 12.9514, 12.8574 and 12.3013 respectively.

scholarly journals Urban Building Change Detection in SAR Images Using Combined Differential Image and Residual U-Net Network

2019 ◽  
Vol 11 (9) ◽  
pp. 1091 ◽  
Author(s):  
Lu Li ◽  
Chao Wang ◽  
Hong Zhang ◽  
Bo Zhang ◽  
Fan Wu
Keyword(s):  
Change Detection ◽  
Rapid Development ◽  
Ratio Method ◽  
Small Scale ◽  
City Management ◽  
Spatiotemporal Resolution ◽  
Sar Images ◽  
Difference Image ◽  
Radar Images ◽  
Log Ratio

With the rapid development of urbanization in China, monitoring urban changes is of great significance to city management, urban planning, and cadastral map updating. Spaceborne synthetic aperture radar (SAR) sensors can capture a large area of radar images quickly with fine spatiotemporal resolution and are not affected by weather conditions, making multi-temporal SAR images suitable for change detection. In this paper, a new urban building change detection method based on an improved difference image and residual U-Net network is proposed. In order to overcome the intensity compression problem of the traditional log-ratio method, the spatial distance and intensity similarity are combined to generate a weighting function to obtain a weighted difference image. By fusing the weighted difference image and the bitemporal original images, the three-channel color difference image is generated for building change detection. Due to the complexity of urban environments and the small scale of building changes, the residual U-Net network is used instead of fixed statistical models and the construction and classifier of the network are modified to distinguish between different building changes. Three scenes of Sentinel-1 interferometric wide swath data are used to validate the proposed method. The experimental results and comparative analysis show that our proposed method is effective for urban building change detection and is superior to the original U-Net and SVM method.

The implications of point source phosphorus management to potable water treatment

1998 ◽  
Vol 37 (2) ◽  
pp. 343-350
Author(s):  
Ralph G. Heath ◽  
Machiel C. Steynberg ◽  
Rita Guglielmi ◽  
Annelie L. Maritz
Keyword(s):  
Waste Water ◽  
Water Treatment ◽  
South African ◽  
Water Intake ◽  
Waste Treatment ◽  
Waste Water Treatment ◽  
Algal Species ◽  
Raw Water ◽  
Urban Settlements ◽  
Informal Urban Settlements

The Vaal River Barrage reservoir is an important source of raw water for Rand Water which supplies at least 10 million people with drinking water daily. Return effluents from waste water treatment works, industries and informal urban settlements in the catchment has resulted in algal problems in the raw water and treatment process. In order to attempt to reduce the effect of eutrophication of South African inland water quality the Department of Water Affairs implemented in 1985 a 1 mg/l ortho-phosphate standard for waste water treatment works effluents. The amount of phosphate originating from the waste treatment works decreased significantly over the 10 years after the standard was implemented even though 40% of the time the works do not comply to the standard. This has resulted in no significant change in the chlorophyll values at Rand Water Intake No. 1. The algal species composition has changed with blue-greens becoming more dominant which has resulted in a higher incidence of algal related problems. The stabilizing of the chlorophyll values is not only as a result of lower ortho-phosphate levels but also due to residence times, turbidity and conductivity. To further reduce the algal concentrations at Rand Water Intake No. 1 the 1 mg/l ortho-phosphate standard will have to be enforced, the standard possibly reduced and diffuse sources managed on a catchment basis.

Utility-small water enterprise partnerships: serving informal urban settlements in Africa

Water Policy ◽  
2004 ◽  
Vol 6 (5) ◽  
pp. 443-452 ◽  
Author(s):  
Cyrus Njiru
Keyword(s):  
Water Utilities ◽  
Sub Saharan Africa ◽  
Water Services ◽  
Water And Sanitation ◽  
Sanitation Services ◽  
Small Water ◽  
Urban Settlements ◽  
Quality Water ◽  
Sub Saharan ◽  
Informal Urban Settlements

Sustainable development cannot be realised when a large proportion of people do not have access to improved water services. Indeed, despite concerted international effort and publicity made in the last two decades to increase coverage of improved water and sanitation services, the number of people without improved water and sanitation services continues to increase. Water utilities are not serving a large proportion of the urban population and small water enterprises (SWEs) have moved to fill the gap. This paper looks at the growing urban water problem and outlines the role played by SWEs in providing water services to those un-served or under-served by water utilities. Typical constraints faced by SWEs are outlined and the rationale for developing utility–SWE partnerships for the benefit of water consumers (customers) is provided. Potential opportunities for developing utility-SWE partnerships are discussed. The paper argues that utility-SWE partnerships can enable SWEs to provide affordable good quality water services to customers, while providing benefit to the utility and thus also assisting the utility to meet its mandate. The paper proposes win–win utility-SWEs partnerships aimed at achieving the objectives of utilities and SWEs while improving water services to customers in informal urban settlements of developing countries, with a focus on sub-Saharan Africa.

scholarly journals Flood Monitoring Based on the Study of Sentinel-1 SAR Images: The Ebro River Case Study

Water ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2454 ◽  
Author(s):  
Francisco Carreño Conde ◽  
María De Mata Muñoz
Keyword(s):  
Risk Mitigation ◽  
Aerial Photographs ◽  
Flood Mapping ◽  
Blue Color ◽  
Economic Activities ◽  
Nature Protection ◽  
Horizontal Polarization ◽  
Sar Images ◽  
Radar Images ◽  
Flood Maps

Flooding is the most widespread hydrological hazard worldwide that affects water management, nature protection, economic activities, hydromorphological alterations on ecosystem services, and human health. The mitigation of the risks associated with flooding requires a certain management of flood zones, sustained by data and information about the events with the help of flood maps with sufficient temporal and spatial resolution. This paper presents the potential use of the Sentinel-1 SAR (Synthetic Aperture Radar) images as a powerful tool for flood mapping applied in the event of extraordinary floods that occurred during the month of April 2018 in the Ebro (Spain). More specifically, in this study, we describe accurate and robust processing that allows real-time flood extension maps to be obtained, which is essential for risk mitigation. Evaluating the different Sentinel-1 parameters, our analysis shows that the best results on the final flood mapping for this study area were obtained using VH (Vertical-Horizontal) polarization configuration and Lee filtering 7 × 7 window sizes. Two methods were applied to flood maps from Sentinel-1 SAR images: (1) RGB (Red, Green, Blue color model) composition based on the differences between the pre- and post-event images; and (2) the calibration threshold technique or binarization based on histogram backscatter values. When comparing our flood maps with the flood areas digitalized from vertical aerial photographs, done by the Hydrological Planning Office of the Ebro Hydrographic Confederation, the results were coincident. The result of the flooding map obtained with the RADAR (Radio Detection and Ranging) image were compared with the layers with different return periods (10, 50, 100, and 500 years) for a selected zone of the study area of SNCZI (National Flood Zone Mapping System in Spain). It was found that the images are consistent and correspond to a flood between 10 and 50 years of return. In view of the results obtained, the usefulness of Sentinel-1 images as baseline data for the improvement of the methodological guide is appreciated, and should be used as a new source of input, calibration, and validation for hydrological models to improve the accuracy of flood risk maps.

scholarly journals Defining a Trade-off Between Spatial and Temporal Resolution of a Geosynchronous SAR Mission for Soil Moisture Monitoring

2018 ◽  
Vol 10 (12) ◽  
pp. 1950 ◽  
Author(s):  
Luca Cenci ◽  
Luca Pulvirenti ◽  
Giorgio Boni ◽  
Nazzareno Pierdicca
Keyword(s):  
Soil Moisture ◽  
Spatial Resolution ◽  
Temporal Resolution ◽  
Added Value ◽  
Sar Images ◽  
Radar Images ◽  
Spatio Temporal ◽  
Set Up ◽  
The Impact ◽  
Hydrological Applications

The next generation of synthetic aperture radar (SAR) systems could foresee satellite missions based on a geosynchronous orbit (GEO SAR). These systems are able to provide radar images with an unprecedented combination of spatial (≤1 km) and temporal (≤12 h) resolutions. This paper investigates the GEO SAR potentialities for soil moisture (SM) mapping finalized to hydrological applications, and defines the best compromise, in terms of image spatio-temporal resolution, for SM monitoring. A synthetic soil moisture–data assimilation (SM-DA) experiment was thus set up to evaluate the impact of the hydrological assimilation of different GEO SAR-like SM products, characterized by diverse spatio-temporal resolutions. The experiment was also designed to understand if GEO SAR-like SM maps could provide an added value with respect to SM products retrieved from SAR images acquired from satellites flying on a quasi-polar orbit, like Sentinel-1 (POLAR SAR). Findings showed that GEO SAR systems provide a valuable contribution for hydrological applications, especially if the possibility to generate many sub-daily observations is sacrificed in favor of higher spatial resolution. In the experiment, it was found that the assimilation of two GEO SAR-like observations a day, with a spatial resolution of 100 m, maximized the performances of the hydrological predictions, for both streamflow and SM state forecasts. Such improvements of the model performances were found to be 45% higher than the ones obtained by assimilating POLAR SAR-like SM maps.

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