The Development of Geomorphic and Hydraulic Complexity Within Streams and its Influence on Fish Communities Following Glacial Recession in Glacier Bay, Alaska

Abstract

Studies of landscape development via primary successional processes are an important area of research for understanding how landscapes evolve into stable, diverse ecosystems. This research sought to assess how geomorphic and hydraulic complexity alter as streams develop following glacial recession. Investigations revealed that younger streams were dominated by fast flowing geomorphic units such as rapids and riffles with little hydraulic or landscape diversity. As stream age increased, however, slower flowing habitat units such as glides and pools became more dominant, resulting in increased geomorphic, hydraulic and riverscape diversity. Determination of these changes in hydromorphic complexity which occur as streams develop, twinned with an assessment of the role of coarse woody debris in creating such complexity at the reach and microscale levels revealed the importance of coarse woody debris in driving these changes. Coarse woody debris was found to influence the development of biocomplexity and interaction between stream terrestrial and floodplain environments. These changes in geomorphic and hydraulic complexity result in the creation and maintenance of instream habitat which biota such as juvenile Pacific salmonids may utilise.