Chapter 10: Indices

Kurzfassung/Abstract

A number of indices has been proposed to assess hydrological or sediment connectivity. These indices operate at different spatial scales, address different types of connectivity (hillslope-channel vs. longitudinal connectivity), are based on different spatial units (raster cell, landform, channel reach, sub-/catchment) and approaches (geomorphological mapping, digital elevation models, network analysis). Temporal constraints for the application of indices exist as connectivity depends on the magnitude of hydrometeorological forcing, and is subject to changes in landscape properties. Connectivity indices are based on variables and assumptions with respect to space and time. We review existing indices of different characteristics (raster, effective catchment area, networks) together with examples, and distinguish two types of their application: descriptive applications in which indices are used to describe spatial patterns of water and sediment (coupled and decoupled) pathways for a point or period of time; and as predictors of connectivity and its consequences (e.g., sediment transfer, sensitivity to change). Opportunities and challenges for research in connectivity indices are discussed.