One of the remarkable characteristics of these basins is their threshold depth, which is specific to each basin. The basins located upstream on the Niger (Moura, Koubaye, Mopti-sud) as well as in the Bani-Niger Mesopotamia (Pondori, Yongari-Mangari and Sebera) start to appear at the contour curve - 1.10 m, i.e. for a flood of 5.50 m at the Mopti gauge. The Pondori even takes shape around -0.90 m and appears completely isolated at -1.10 m. The three basins directly dependent on Bani and Mopti-nord have a threshold contour at -1.20 m. The basins of the center of the Delta, Tenenkou (-1.40 m), Kakagnan and Kadial (-1.60 m) are located deeper than the southern basins. Finally, the threshold contour for Toggere Koumbe is at -2.00 m and the Débo-Walado, which we have not separated from the Konna basin, has a threshold contour at -2.20 m. These differences in threshold contours between basins are linked to the morphology of the Delta and result from the tectonic move towards the north-east, which caused all channels to move eastwards and resulted in the Peroudji channels from Ouro Modi to Dialloubé being deserted and replaced by the current Niger flow through Mopti and Konna. This explains the lower subsidence of the southern part of the Delta floodplain, which is accompanied by a more intense alluvium deposition, perfectly in agreement with the morphological study by Jean Gallais: “ The Inner Niger Delta and its borders: a morphological study ”, (Memoirs and documents of the CNRS, vol. 3, 1967, 54 p., 5 maps, p 144) which described the southern basins as "hanging basins" compared to those, deeper, of the center of the Delta and, a fortiori , that of Débo-Walado. 2 –The vegetal landscapes: The thresholding of the Veg7k3 matrix also allows us to separate the vegetal landscapes of the Delta into major categories: - the dry lands bordering the Delta and the large islands within the floodplain - the high plains, shallowly flooded (between -0.0 m and -0.60 m) - the moderately flooded plains and channels (between -0.60 m and -1.50 m) - the deeply flooded plains and channels (= <-1.50m) The flood depth contours oppose the floodplains characterized by moderate-to-deep flooding of plains and channels, mainly situated along the Diaka, and those characterized by shallow floods, mainly located in the south (Diafarabé region), towards the upstream limits of the active Delta. In the south, the flooded erg of Samaye extends towards the Pondori and Yongari-Mangari basins, which it contributes to separate. The erg of Femaye further extends to the east, forcing the Bani river to bend its course. The high plains of Soye, north of Femaye, contribute to clearly separate the southern basins from the Bani-Niger Mesopotamia. Finally, a set of fossil levees form uplands along an SSW - NNE alignment. They stretch from the Moura basin to the south of Lake Débo and testify to the existence of a former course of the Niger which is now fossilized. This helps to isolate the basins in the west of the Delta, which, from Ténenkou onwards, organize and communicate through a set of deep flood plains finally joining the Wallado-Débo. These deep plains do not exist in the south, and are almost absent in the east at Mopti and are only found again to a certain extent in the northeast, near Konna. Map 1 : The main inner Delta plant landscapes