Habitat - Guidelines
Date Published: April 04, 2002
Number of Pages: 130
Author(s): G. Mathias Kondolf, Matt Smeltzer, Lisa Kimball, Center for Environmental Design Research
The state-of-the-knowledge white paper on this subject was completed December 2001. Issues addressed in the white paper include hydrologic and ecological effects of in-channel bar scalping, risks and avulsions associated with floodplain pits, freshwater dredging, instream sediment sumps and gravel pits, gravel removal.
Sediment is mechanically removed from river channels in Washington State for a variety of reasons: to improve navigation, agricultural drainage, flood control, channel stability, and production of construction aggregate. In this white paper, we review the scientific information regarding the effects of these activities.
Extraction of sand and gravel for construction aggregate is the largest mining industry in most states – not only in volume but also in value. As the environmental impacts of aggregate extraction from river channels become increasingly well understood, the practice has received increased scrutiny, especially in salmon-bearing rivers and streams. For Washington State, the supply of sand and gravel from various sources by geologic province, and environmental impacts of extraction from channels and floodplains have been summarized in excellent reviews by Dunne et al. (1981), Bates (1992), Collins (1995), and Norman et al. (1998). The purpose of this report is to build upon existing literature for Washington and elsewhere to summarize current scientific information regarding the environmental effects of mining gravel and sand for construction aggregation from rivers and streams, along with the effects of other freshwater dredging. The emphasis is on effects on salmonids in their various freshwater-based life stages, to provide a scientific basis for future development of guidelines that will be protective of the resource.
This document does not make policy recommendations, but summarizes the scientific literature and unpublished research on gravel mining effects in Washington state and elsewhere. It also draws upon discussions with resource managers, site visits, and analysis of historical aerial photographs and maps of selected sites. There is relatively little literature on this subject in international, peer-reviewed journals, though the body of work expands once agency technical reports and similar “gray” sources are included. As an efficient, easily read and comprehended format for presenting the literature review, we prepared a table summarizing our literature review (Appendix A), which complements the topical-based review in the text. The purpose of this white paper is to summarize the scientific information that will serve as the basis for future guidance documents.