The physical effect of logging on salmon streams : a summary report covering a 5-year calilbration period on four streams in Southeast Alaska /

Abstract

The principal and most valuable industry of Alaska has been the salmon fisheries. Future development of Southeast Alaska, however, will depend on an increasing utilization of its important forest resource. The fisheries resource and the timber resource are intimately related. Reliable answers are therefore needed as to whether large-scale pulptimber logging is harmful to the spawning facilities of salmon streams. The Alaska Forest Research Center began a program of research in 1949 to relate logging practices by Forest Service standards to changes in the large-scale physical factors of the stream environment. ±' The study is divided into two parts: (1) collection of quantitative information on type and extent of physical change which takes place in these streams prior to logging, and (2) quantitative change following logging. Four streams, located in the Kasaan Bay area, Prince of Wales Island, were selected for long-term study. Two of the study watersheds will be logged; two will not be logged. Measurements are being made of such factors as climate, streamflow, storms and associated runoff, base flow, water temperature, stream channel change, sedimentation, and others. Rate and characteristics of streamflow influence both the physical and the biotic elements of the stream. This phase of the study will determine the effect of timber harvest on stream runoff. Basic data collected include a continuous record of stream height, discharge velocity associated with stream height, snow and ice conditions, analysis of storm flow, and groundwater depletion. Data are presented showing mean monthly stream height, mean monthly discharge, the relationship between rainfall and runoff, analysis of flood peaks, ratio of maximum to minimum stream discharge, and groundwater depletion.