Ordering interfluves: a simple proposal for understanding critical zone evolution and function

The Earth’s critical zone (CZ) is the integrated life-supportive system between the atmosphere and the deepest bio-geoweathering front of geologic materials. At the Calhoun Critical Zone Observatory (CCZO) in the Carolina Southern Piedmont, we propose an ordering system for upland interfluves that is a reciprocal of the widely used Hortonian stream order system. Interfluve order hypothetically controls and informs us about the evolution of hydrologic, geomorphologic, biogeochemical, and biotic systems; CZ response to historic land use change; and the contemporary functioning and management of the CZ. With LiDAR and DEM mapping enabling new quantitative research of landscape and critical zone structure and function, we propose that many physiographic regions will benefit from a system that orders interfluves.