Mapping wetland water depths over the central Congo Basin using PALSAR ScanSAR, Envisat altimetry, and MODIS VCF data

Lee, Hyongki; Yuan, Ting; Jung, Hahn Chul; Beighley, R. Edward

doi:10.1016/j.rse.2014.11.030

Cited by 58 publications

(40 citation statements)

References 23 publications

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“…Among available calibrated products from SNAP, such as amplitude, intensity, beta-nought, and sigma nought, we selected sigma-nought since preliminary statistical tests showed that sigma-nought provides a better separation between water and land surfaces. Some previous studies have also used sigma-nought images for surface water mapping [48,49]. In order to reduce speckle noise, multilooking and speckle filtering with a Median filter and window size of 5 × 5 pixels was used after some preliminary tests on the size of window (3 × 3 or 5 × 5) and with some types of filtering (Mean, Median, Gamma Map, Lee, Frost, and Refined Lee).…”

Section: Methodsmentioning

confidence: 99%

A Method for Automatic and Rapid Mapping of Water Surfaces from Sentinel-1 Imagery

et al. 2018

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Abstract:Reliable information about the spatial distribution of surface waters is critically important in various scientific disciplines. Synthetic Aperture Radar (SAR) is an effective way to detect floods and monitor water bodies over large areas. Sentinel-1 is a new available SAR and its spatial resolution and short temporal baselines have the potential to facilitate the monitoring of surface water changes, which are dynamic in space and time. While several methods and tools for flood detection and surface water extraction already exist, they often comprise a significant manual user interaction and do not specifically target the exploitation of Sentinel-1 data. The existing methods commonly rely on thresholding at the level of individual pixels, ignoring the correlation among nearby pixels. Thus, in this paper, we propose a fully automatic processing chain for rapid flood and surface water mapping with smooth labeling based on Sentinel-1 amplitude data. The method is applied to three different sites submitted to recent flooding events. The quantitative evaluation shows relevant results with overall accuracies of more than 98% and F-measure values ranging from 0.64 to 0.92. These results are encouraging and the first step to proposing operational image chain processing to help end-users quickly map flooding events or surface waters.

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Section: Methodsmentioning

confidence: 99%

A Method for Automatic and Rapid Mapping of Water Surfaces from Sentinel-1 Imagery

et al. 2018

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“…There have also been a number of studies of river water chemistry (Laraque et al 2001(Laraque et al , 2009, the geological origins of the basin (Daly et al 1992;Crosby et al 2010;Kadima et al 2011;Buiter et al 2012), remote-sensing-based studies of hydrology and vegetation distribution (Mayaux et al 2004;Vancutsem et al 2009;Bwangoy et al 2010;Jung et al 2010;Betbeder et al 2014;Lee et al 2015), and the contested origins of Lac Télé (Master 2010). None of these studies have taken account of the status of the Cuvette Centrale as a major peatland complex, but many of them are, with hindsight, relevant to understanding the system as a whole.…”

Section: Study Areamentioning

confidence: 99%

Congo Basin peatlands: threats and conservation priorities

Dargie

Lawson

Rayden

et al. 2018

Mitig Adapt Strateg Glob Change

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The recent publication of the first spatially explicit map of peatlands in the Cuvette Centrale, central Congo Basin, reveals it to be the most extensive tropical peatland complex, at ca. 145,500 km 2 . With an estimated 30.6 Pg of carbon stored in these peatlands, there are now questions about whether these carbon stocks are under threat and, if so, what can be done to protect them. Here, we analyse the potential threats to Congo Basin peat carbon stocks and identify knowledge gaps in relation to these threats, and to how the peatland systems might respond. Climate change emerges as a particularly pressing concern, given its potential to destabilise carbon stocks across the whole area. Socio-economic developments are increasing across central Africa and, whilst much of the peatland area is protected on paper by some form of conservation designation, the potential exists for hydrocarbon exploration, logging, plantations and other forms of disturbance to significantly damage the peatland ecosystems. The low level of human intervention at present suggests that the opportunity still exists to protect the peatlands in a largely intact state, possibly drawing on climate change mitigation

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“…Building on their remote sensing approach, Lee et al . [] generated water depth maps over the Cuvette Centrale by combining imaging and altimetry methods in a linear regression model. They validated their mapped depth changes with interferometric SAR measurements of water level changes.…”

Section: Hydrologic Measurements and Related Modelsmentioning

confidence: 99%

Opportunities for hydrologic research in the Congo Basin

et al. 2016

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We review the published results on the Congo Basin hydrology and summarize the historic and ongoing research. Annual rainfall is ~1900 mm/yr along an east‐west trend across the basin, decreasing northward and southward to ~1100 mm/yr. Historic studies using lysimeters, pans, and models suggest that the annual potential evapotranspiration varies little across the basin at 1100 to 1200 mm/yr. Over the past century, river discharge data have been collected at hundreds of stream gauges with historic and recent data at 96 locations now publicly available. Congo River discharge at Kinshasa‐Brazzaville experienced an increase of 21% during the 1960–1970 decade in comparison to most other decades. Satellite altimetry measurements of high and low flows show that water levels in the “Cuvette Centrale” wetland are 0.5 m to 3.0 m higher in elevation than the immediately adjacent Congo River levels. Wetland water depths are shallow at about a meter and there does not appear to be many sizable channels across the “Cuvette”; thus, wetland flows are diffusive. Cuvette waters alone are estimated to emit about 0.5 Pg CH4 and CO2 equivalents/yr, an amount that is significant compared to global carbon evasions. Using these results, we suggest seven hypotheses that focus on the source of the Cuvette waters and how these leave the wetland, on the river discharge generated by historic rainfall, on the connection between climate change and the rainfall‐runoff generated by the migrating “tropical rainbelt,” on deforestation and hydroelectric power generation, and on the amount of carbon emitted from Congo waters.

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Mapping wetland water depths over the central Congo Basin using PALSAR ScanSAR, Envisat altimetry, and MODIS VCF data

Cited by 58 publications

References 23 publications

A Method for Automatic and Rapid Mapping of Water Surfaces from Sentinel-1 Imagery

A Method for Automatic and Rapid Mapping of Water Surfaces from Sentinel-1 Imagery

Congo Basin peatlands: threats and conservation priorities

Opportunities for hydrologic research in the Congo Basin

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