Date of Award

Winter 2012

Project Type

Thesis

Program or Major

Civil Engineering

Degree Name

Master of Science

First Advisor

Thomas Ballestero

Abstract

Wood is an integral part of stream health. Large woody debris (LWD) creates habitat and refuge for both fish and invertebrates. Knowing the effects of LWD on stream geomorphology is helpful for stream restoration projects so that the placement of wood mimics the natural condition. This study compares conventional-sediment riffles to wood-dominated riffles in southeastern, coastal New Hampshire. Wood riffles are fast-moving sections of the stream where the presence of LWD creates a local change in stream slope. Past studies have found that log steps are wider, shallower, steeper, more closely spaced, have finer bed sediments than conventional riffles on the same system.

Field surveys were conducted on wood-riffle and conventional sediment riffle sections of several streams in the seacoast region of New Hampshire. Geomorphic data were collected as well as regional geomorphic data from a Rapid Geomorphic Assessment from 2011. Properties of the wood riffles were compared to the representative reference riffle sections and to the regional data. Analysis shows that wood riffles are wider, have larger area, are finer upstream, and coarser downstream than conventional riffles. They also have more variation in slope and spacing than the reference sections.

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