AbstractUnderstanding patterns of vegetation degradation in saline catchments has been a major challenge to ecohydrology researchers in the conservation biology, geomorphology and hydrology disciplines. Hydrologists have measured streamflow quantity and quality at point locations and modelled at the landscape or macro‐scale. Botanists have investigated species diversity, structure and patterns at the micro‐scale in transect studies. Yet, the reach‐scale is widely recognized as the most appropriate scale for management and considering geomorphology. As a result, links between streamflow salinity and vegetation condition and river health remain poorly understood in a spatial sense. This study uses digital multi‐spectral imagery (DMSI) collected along a freshening downstream salinity gradient in a southwestern Australian catchment affected by secondary dryland salinity. DMSI was collected over 59 km in a 1200‐m swath at the micro‐scale (2‐m pixels), and calibrated against field transect data from 12 sites across three sections (degraded, transitional and ‘locally healthy’) to map vegetation condition. Results show that measures of mean annual salinity cannot account for variability in vegetation condition, but peak salinity concentration maintained over a length of time similar to greenhouse trials of plant mortality (∼60 days) appears to be a physiologically meaningful descriptor of streamflow salinity. The 60‐day peak salinity concentration showed high correlation to patterns of vegetation condition and published plant salinity tolerance values. Remote‐sensed imagery that captures vegetative condition in combination with physiologically meaningful descriptors of streamflow salinity provides a powerful tool to identify the spatial patterns of vegetation degradation at meaningful management scales within a saline catchment. Copyright © 2010 John Wiley & Sons, Ltd.