Application of modern geomorphic concepts for understanding the spatio-temporal complexity of the large Ganga river dispersal system

Significant advances have been made towards understanding the dynamics of geomorphic systems through the development of new concepts. In the last two decades, these developments were partly guided by the change in the scale of geomorphic analysis from local (landform) to regional (landscape) scale and partly due to the emergence of new scientific tools and quantitative models. The process-based understanding of some geomorphic systems of the Indian subcontinent has also advanced in a significant way and a substantial dataset is now available, especially on the Ganga river system. However, conceptual advancements in geomorphic studies have not been incorporated with the available database on large river systems, especially the Ganga river basin. This article attempts to provide a brief review of geomorphic concepts, i.e. scale, magnitude–frequency, equilibrium, threshold, hierarchy, sensitivity, connectivity, nonlinearity, complexity and multidisciplinarity, and their application for understanding the geomorphology of a large river system, i.e. the Ganga river system. This re-evaluation and synthesis of the geomorphic data of the Ganga riverscape provides useful insights into the dynamics of this multi-scale dispersal system, and thereby also helps in the identification of gaps in knowledge that need to be addressed on a priority basis. The major gaps at longer timescales (10–10 years) include lack of understanding of connectivity in river response to external forcing, the quantification of threshold of geomorphic change, and the integration of scales in terms of forms and processes. At modern timescale, the major challenge is to integrate the geomorphic dataset with ecological and hydrological attributes in order to develop a holistic understanding of rivers for their management.