Surveillance et cartographie des plans d'eau et des zones humides et inondables en régions arides avec l'instrument VEGETATION embarqué sur SPOT-4

Gond, Valéry; Bartholomé, Étienne; Ouattara, Frédéric; Nonguierma, André; Bado, L.A. Calvo

doi:10.1080/0143116031000139908

Cited by 47 publications

(31 citation statements)

References 15 publications

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“…Moreover, some ponds, like Ebang Mallam, split into several small ponds, which size may be smaller than the spatial resolution of MODIS. This is in line with previous studies using moderate and low resolution sensors (Verdin et al, 1996;Gond et al, 2004;Haas et al, 2009), which concluded that surface estimation is accurate above a given threshold of a few ha or tens of ha, allowing pure pixels to be present. Ponds' size at the end of the wet season, typically from September to November, is therefore preferred to carry out the analysis of the long term changes of the flood in ponds.…”

Section: Assessments Of the Classificationssupporting

confidence: 79%

“…To date, attempts have been made to map the pond floods and to estimate flooded areas either at one date, at a relatively high spatial resolution on the basis of one LAND-SAT or SPOT-HRV image (Liebe et al, 2005;Lacaux et al, 2007) or at a lower resolution using time series of NOAA-AVHRR, SPOT-VGT or MODIS data (e.g. Gond et al, 2004;Haas et al, 2009;Verdin et al, 1996). Beside, the spectral response of surface water has received relatively little attention so far in this region, with a few exceptions like Lacaux et al (2007).…”

Section: Introductionmentioning

confidence: 99%

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Less rain, more water in ponds: a remote sensing study of the dynamics of surface waters from 1950 to present in pastoral Sahel (Gourma region, Mali)

Gardelle

Hiernaux

Kergoat

et al. 2010

Hydrol. Earth Syst. Sci.

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Abstract. Changes in the flooded area of ponds in the Gourma region from 1950 to present are studied by remote sensing, in the general context of the current multi-decennial Sahel drought. The seasonal and interannual variations of the areas covered by surface water are assessed using multidate and multi-sensor satellite images (SPOT, FORMOSAT, LANDSAT-MSS, -TM, and -ETM, CORONA, and MODIS) and aerial photographs (IGN). Water body classification is adapted to each type of spectral resolution, with or without a middle-infrared band, and each spatial resolution, using linear unmixing for mixed pixels of MODIS data. The high-frequency MODIS data document the seasonal cycle of flooded areas, with an abrupt rise early in wet season and a progressive decrease in the dry season. They also provide a base to study the inter-annual variability of the flooded areas, with sharp contrasts between dry years such as 2004 (low and early maximal area) and wetter years such as 2001 and 2002 (respectively high and late maximal area).The highest flooded area reached annually greatly depends on the volume, intensity and timing of rain events. However, the overall reduction by 20% of annual rains during the last 40 years is concomitant with an apparently paradoxical large increase in the area of surface water, starting from the 1970's and accelerating in the mid 1980's. Spectacular for the two study cases of Agoufou and Ebang Mallam, for which time series covering the 1954 to present period exist, this increase is also diagnosed at the regional scale from LANDSAT data spanning 1972-2007. It reaches 108% between September 1975 and 2002 for 91 ponds identified in central Gourma. Ponds with turbid waters and no aquatic vegetation are mostly reCorrespondence to: P. Hiernaux (pierre.hiernaux@cesbio.cnes.fr) sponsible for this increase, more pronounced in the centre and north of the study zone. Possible causes of the differential changes in flooded areas are discussed in relation with the specifics in topography, soil texture and vegetation cover over the watersheds that feed each of the ponds. Changes in rain pattern and in ponds sedimentation are ruled out, and the impact of changes in land use, limited in the area, is found secondary, as opposed to what has often been advocated for in southern Sahel. Instead, major responsibility is attributed to increased runoff triggered by the lasting impact of the 1970-1980's droughts on the vegetation and on the runoff system over the shallow soils prevailing over a third of the landscape.

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Section: Assessments Of the Classificationssupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Less rain, more water in ponds: a remote sensing study of the dynamics of surface waters from 1950 to present in pastoral Sahel (Gourma region, Mali)

Gardelle

Hiernaux

Kergoat

et al. 2010

Hydrol. Earth Syst. Sci.

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show abstract

“…The spectra of water are modified by suspended solids, coloured dissolved organic matter and water plants, primarily shifting the peak of the reflectance from shorter wavelengths towards the red light (Cavalli et al, 2009). This spectral characteristic is used to define water bodies by means of the Normalized Difference Vegetation Index (NDVI) (Frazier and Page, 2000;Gond et al, 2004). Using the ratio of the red band and the near infrared band of NOAA AVHRR Sheng et al (1998) could monitor floods by determining specific thresholds.…”

Section: Data Setsmentioning

confidence: 99%

Meteorological characteristics and potential causes of the 2007 flood in sub‐Saharan Africa

Paeth

Fink

Pohle

et al. 2011

Intl Journal of Climatology

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ABSTRACT:In August and September 2007 media and aid organizations reported on a severe flood in large parts of sub-Saharan Africa caused by a sequence of extreme rain events. However, the reporting was partly controversial and much was speculated about how unusual the flood event was. Here, we analyse various observational data sets in order to assess and to compare the spatio-temporal characteristics and intensity of the flood and the associated rain events. The return times are estimated from daily precipitation time series at fine spatial resolution, and the potential causes are disclosed in a global and regional context.Satellite data reveal that the flood was not large scale but confined to the main river basins in sub-Saharan West Africa. Nonetheless, abundant rainfall prevailed over large parts of Western Africa extending north into the Western Sahara, particularly during the second half of August and the beginning of September 2007. In detail, various precipitation data sets differ considerably in terms of the monthly anomalies, demonstrating the difficulty to delineate meteorological extreme events even at a sub-continental scale and during the most recent past. Return times typically range between 1 and 50 years with high spatial heterogeneity but amount to 1200 years in the regional mean over the Upper Volta Basin. Among the potential causes we identify a La Niña event in the tropical Pacific, anomalous heating in the tropical Atlantic coming along with a greater depth of the monsoonal westerlies, and enhanced activity of African easterly waves, both evident in 2-6 day zonal wind and outgoing longwave radiation variance anomalies.

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“…Así se entiende en Gond et al (2004) al plantear que los ND calibrados se convierten a radianza (la proporción de energía que recibe el sensor) usando la pendiente, los parámetros de compensación a partir del coeficiente de conversión de unidad, disponibles para cada banda en los metadatos, así como los parámetros de ganancia conocidos.…”

Section: Correcciones Radiométricasunclassified

Comportamiento Temporal Y Espacial Del Bosque Ribereño en El Curso Bajo Del Río Portoviejo Y La Quebrada Chilán, Provincia De Manabí, Ecuador

Pacheco

2017

Rev. Int. Contam. Ambie.

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Palabras clave: restauración ecológica, tecnologías SIG, agricultura y ganadería, reemplazo de bosques RESUMEN El objetivo de este trabajo fue estudiar y comparar, en términos espaciales y temporales, la cobertura de bosques ribereños en el curso bajo del río Portoviejo y la Quebrada Chilán mediante la aplicación de herramientas de información geográfica, sensores remotos y monitoreos de campo. Estos bosques se desarrollan a lo largo de dos cursos de agua asentados en cuencas contiguas, que desembocan en el Pacífico ecuatoriano, entre Jaramijó y San Clemente. Los resultados muestran que en el curso bajo del río Portoviejo los bosques ribereños tuvieron bajos porcentajes de cobertura en los años 1998, 2002, 2009, 2011 y 2013, mientras que en la quebrada Chilán aumentaron significativamente desde 1998 hasta 2014, cubriendo ambos márgenes del cauce en todo su recorrido. El creciente desarrollo agrícola y ganadero es causa principal por la cual desapareció gran parte del bosque ribereño en los márgenes del río Portoviejo. En la quebrada Chilán, en contraste, no se aprecia actividad económica que conlleve a la ocupación espacial y al reemplazo del bosque. Sobre la base de los resultados encontrados y por la importancia ecológica de estas áreas naturales, se discuten y plantean estrategias para la conservación de bosques ribereños en la quebrada Chilán, como también para restaurar áreas de bosques ribereños en el curso del río Portoviejo reemplazadas por cultivos y pastizales. Dentro de las propuestas de restauración se incluyen acciones tendientes a recuperar su trayectoria original, tomando como referencia pequeños parches de vegetación del mismo tipo que aún se conservan en el área de estudio.Key words: ecological restoration, GIS technologies, agriculture and livestock, forest replacement ABSTRACTThe aim of this work was to study and compare, in spatial and temporal terms, the coverage of riparian forests in the lower reaches of the Portoviejo River and the ravine Chilán through the application of tools of geographical information systems, remote sensing and field monitoring. These forests are developed along two streams seated in adjacent basins, which flow into the Ecuadorian Pacific between Jaramijó Rev. Int.

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Surveillance et cartographie des plans d'eau et des zones humides et inondables en régions arides avec l'instrument VEGETATION embarqué sur SPOT-4

Cited by 47 publications

References 15 publications

Less rain, more water in ponds: a remote sensing study of the dynamics of surface waters from 1950 to present in pastoral Sahel (Gourma region, Mali)

Less rain, more water in ponds: a remote sensing study of the dynamics of surface waters from 1950 to present in pastoral Sahel (Gourma region, Mali)

Meteorological characteristics and potential causes of the 2007 flood in sub‐Saharan Africa

Comportamiento Temporal Y Espacial Del Bosque Ribereño en El Curso Bajo Del Río Portoviejo Y La Quebrada Chilán, Provincia De Manabí, Ecuador

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