Modelling alluvial fan morphology

A mathematical model which estimates the scale-independent sediment surface profile of alluvial fans has been developed. This model utilizes a diffusi ve sediment transport model and an unsteady, radial flow, conservation rela tionship. These equations are approximately solved assuming a quasi-steady- state closure with appropriate modelling assumptions for two end member fan types: (1) fans where most of the fan surface is depositionally active (de noted here as 'homogeneous') and (2) fans characterized by channelling and sediment sorting processes. The fundamental result for these two fan types is a dimensionless sediment profile relationship which approximates most fa n surfaces. The model suggests that the overall dimensionless morphology of alluvial fans is governed more by fundamental diffusion principles in sedi ment deposition than by individual environmental or basin characteristics. Additionally, this work potentially can be extended to model temporal varia tion in fan development. Preliminary comparison with alluvial fan profiles is reasonable, indicating that this model provides useful qualitative and q uantitative information relating to alluvial fan process and morphology. Co pyright (C) 1999 John Wiley & Sons, Ltd.