A Multi-Reach Comparison of Geomorphic Complexity and Hyporheic Exchange in Agricultural and Urban Streams

The influence of hyporheic flow on the thermal, nutrient and hydraulic regimes of streams is well known, but quantifying the components of geomorphic complexity that have the greatest influence on hyporheic exchange is a challenge. To explore this relationship, we surveyed three unique segments on each of two streams, one in a Colorado Front Range urban setting and the other in a mountainous agricultural region in north central Colorado. Each segment was chosen for its distinctive geomorphic setting and historical human modification; the urban stream showing various levels of stabilization and planform alteration, and the agricultural stream subject to variable cattle grazing practices. All segments were surveyed using a detailed protocol for characterizing physical complexity in terms of the spatial distribution of habitat units with distinct combinations of geomorphic, substrate, and hydraulic attributes. Results from this research may shed light on restoration strategies that could enhance hyporheic flow.