Establishment of the river pattern unit representation model based on rough set rules

The alluvial channels in the middle and lower reaches of the Yellow River are scattered and multibranched, with complex changes in river morphology. Traditional geometric parameter descriptions can no longer meet the need for expressing more refined river morphological characteristics. In this paper, the river morphological unit is used as the basic element, and factors are selected from four aspects—area, shape, aggregation, and diversity—to characterize the spatial distribution and morphological structure of river islands. Leveraging the advantages of rough set theory in descriptor reduction and generating interpretable rules, a river morphological unit expression model composed of boundary-level and internal-level descriptors was established. The results show that there are nine expression models for river morphological unit categories, and the accuracy of these models in representing the Yellow River exceeds 92%. In addition, three rivers were randomly selected for model validation. The results indicate that the model can effectively represent both straight and meandering river morphological units, with an accuracy of over 95% in representing branched river morphology.