Riverscape interpretation in Great Basin National Park: A geomorphic assessment of streams and riparian areas

Shahverdian, Scott; Schook, Derek

doi:10.36967/2307540

Streams can be challenging systems to manage due to their dynamic nature and complex feedbacks between hydrologic, geomorphic, and biological processes that operate over a range of timescales. Stream-riparian ecosystems, also known as riverscapes or river corridors, are affected by events ranging from single storms to large-scale landscape disturbances such as wildfires and landslides. Understanding riverscape dynamics is necessary for identifying potential causes of their degradation, appropriate management actions, and potential restoration strategies. Developing appropriate expectations requires a conceptual understanding of how riverscape conditions and processes vary across the watershed. However, effective interpretation of riverscapes often requires specific expertise related to landscape processes and fluvial geomorphology. This report presents core fluvial geomorphic concepts and develops a reach type classification for riverscapes across Great Basin National Park (GRBA). We begin by identifying landscape factors and basic fluvial geomorphic principles needed to interpret stream forms and processes in GRBA, differentiating the physical characteristics of stream reaches and the processes that maintain them. The report then describes the forms and dynamics of seven different reach types in GRBA. We relied on a combination of remotely sensed data and field observations to categorize GRBA streams. We identify and describe attributes and dominant processes shaping each reach type. Many GRBA streams are found in steep valleys with coarse substrates. These streams have low sensitivity to disturbances, meaning that they are resistant to change. GRBA also supports a limited number of lower-gradient reaches with finer substrates that are more sensitive to disturbances. GRBA streams have variable degrees of confinement, affecting their capacity for lateral adjustment through channel migration or activation of alternative parallel channels. Large wood is important in creating habitat features and influencing stream dynamics throughout GRBA, although the specific processes and habitats influenced by wood vary across reach types. Glacial history and modern hillslope processes are also important features of current stream processes in GRBA, causing the stream reaches in broader valleys to have unusually low sensitivity to disturbance and allowing them to resist disruption to core fluvial processes. This document provides more of an introductory framework and conceptual foundation, rather than serving as a complete how-to manual for managing park streams. Any specific management questions encountered in the future are likely to require more focused investigation. Our goal is that this document will further build a foundation that leads to wise interpretations, expectations, and decisions regarding river management in GRBA.

Riverscape interpretation in Great Basin National Park: A geomorphic assessment of streams and riparian areas

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