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Permeability of alluvial fan deposit is variable with how fully matrix is packed, matrix packing level. In this study, undisturbed gravelly samples are divided into two parts by optimum calculation based on matrix packing levels.Matrix part is one part in which matrix is fully or almost fully packed, and water passage part is the other part in which matrix isn't packed enough. A distribution model of permeability is induced by the arithmetic mean of the permeability of matrix and water passage parts weighted by their thickness. In the Toyohira-gawa river Alluvial fan, especially on Sapporo-surface, the optimum equation by setting four matrix packing levelsⅠto Ⅳ can calculate the permeability to be nearly equal, ranged between half and double, to the measured one. This model is effective to estimate in-situ permeability of alluvial fan deposit. In addition, this model is expected to be applied to estimate heterogeneity by inferring the detailed distribution of permeability. The vertical distribution of permeability in the Toyohira-gawa river Alluvial fan indicates strong heterogeneity between adjacent points. The variogram of log(K') reveals that the macroscopic heterogeneity occurs at observation distance in excess of 5 to 10 meters.