Modified soil moisture index (BFi) (25 m grid)

The modified soil moisture index (BFi) represents a measure of the relief-related potential moisture conditions of the soil. It is calculated on the one hand from the complex relief parameter catchment area size, i.e. the amount of water available through drainage and on the other hand from the local relief parameter slope. The inclination controls the flow velocity and thus the dwell time of the draining water. Further details on the process (without modification) can be found at Böhner & Köthe (2003). The modified soil moisture index is a powerful relief parameter. It is possible, among other things, that wide valley soils have a uniform high soil moisture index and not as for Moore et al. (1993) High indices remain concentrated only on the narrow drain lines in the valley floors (cf. Böhner & Köthe 2003). The modification of the soil moisture index consists primarily of weighting the slope inclination. The weighting factor used is 4 (default value is 2). Although the relatively high weighting factor 4 leads to the fact that the soil moisture index is rather undifferentiated in the mountain country and the end moraines of the geest already have similar low values as the mountain country, all very flat inclined areas are strongly differentiated. Since Lower Saxony has predominantly a flat inclined relief and since the connection soil-relief is usually stronger in groundwater sites, a high weighting factor has been chosen. Böhner, J. & Köthe, R. (2003): Soil regionalisation and process modelling: Instruments for soil protection. — PeterM. Geogr. Mitt., 147, 2003/3: 72-82; Gotha