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Floodplain vegetation response to interannual flood regime through coupled in situ and remote sensing data

Author(s): Application on the Lower Volga river (Russia)
Congress: 2008
Author(s): Tatiana Balyuk, Pascal Kosuth, Thierry Tormos
(1) Cemagref, UMR TETIS (Cemagref – CIRAD – ENGREF AGROPARISTECH), Maison de la Télédétection, 500 rue Jean- François Breton, 34093 Montpellier, Cedex 5 France ; Tel. (33) 04 67 54 87 54 ; Fax (33) 04 76 54 87 00 ; email : balyuk@teledetection.fr

Keyword(s): Floodplain, floodplain vegetation, Volga, inundation, remote sensing
AbstractThe Volga river basin includes 38% of the total agricultural area in Russia. Discharge regulation of the Volga river started in 1937. Guided by the large scale expansion of human economic activities in the basin, an additional 10 major dams were constructed between 1940 and 1986 along the course of the river. The Volga-Akhtuba floodplain extends downstream of the last dam. Surrounded by vast zones of dry steppe and semi-desert this floodplain is an oasis for all forms of life. However, it is very sensitive to human impact, and particularly to the change in river regime caused by flow regulation. Monitoring and understanding ecological processes and changes at the landscape scale is a major challenge for the preservation of this ecosystem The main objective of this work is to develop methods based on satellite imagery coupled with field observations to assess the impact of interannual flood regime on floodplain vegetation. This study is based on a combination of spatial data from satellite images and field observations of morphological features and vegetation in a number of cross-sections over the floodplain. Additionally, as flooding is a key driver for the development of floodplain morphology and vegetation, hydrologic data (water level time series) are analysed. Vegetation evolution from a bare surface up to soft-wood forest is a slow process, therefore two time scales are under consideration : - 30 year evolution of the vegetation, using Landsat imagery (1974-2002) - 7 year detailed analysis of the relation between hydrology and vegetation, using daily hydrologic data and 16 days MODIS images (2000-2006) Different types of water bodies were studied : permanent water in the main channel, permanent water in the lakes of the central floodplain, temporary water bodies in the inundated zone. NDVI index and Near Infra Red channels were used for separation of terrestrial ecosystems. Relation between the area of the inundated zone and the river discharge through Volgograd dam was calculated. Vegetation classification was made on the base of Landsat images with 25 legend classes, that included 18 general types of plant communities. Satellite images provide the basis for a reliable analysis of the flooding in the Lower Volga region over the last 7 years. MODIS images give possibilities for monitoring of vegetation changes both during seasonal cycles and at interannual time-scale. Area of inundation shows correlation with discharge from Volgograd dam.
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