We present a comprehensive approach for validating braided-stream models and apply it to a specific cellular braided-stream model. The approach involves quantitative comparison of modeled and natural braided streams in terms of two main aspects: the sequential organization of their plan patterns studied using their state-space characteristics and the hierarchical organization of their patterns studied in the framework of self-affine scaling. These two aspects of braided streams are complementary to each other and taken together provide a sensitive test of the validity of a model of braided streams. The simple model we examine produces patterns that are similar to those of natural braided rivers in terms of both sequential organization and self-affine scaling. This finding supports the conclusion that the nonlinear interactions between water and sediment in the model are the primary mechanisms responsible for shaping braided rivers in nature. ¿ 1998 American Geophysical Union