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Where does the river transport wood? Longitudinal change in woody debris over a  forested channel network

Amy Nicoll, M.Sc. Candidate Supervised by Lori Daniels and Marwan Hassan


Outline • Context and objectives • Study sites • Methods • Stream dimensions • Wood survey

• Results • • • •

Stream characteristics Changes in position class Change in decay class Proportion involved in logjams

• Next steps

Introduction

Methods

Results

Next Steps


Woody debris in streams

Creates pools and changes flow

Provides habitat for fish

Influences sediment transport

Regulates nutrient transport Image: Steve Adams 2009

Introduction

Methods

Results

Next Steps


Objectives 1. Identify zones of wood transport over a small  stream network 2. Quantify changes in wood characteristics and  functions associated with transport initiation 3. Compare wood residence time in transported and  non‐transported wood regimes 

Introduction

Methods

Results

Next Steps


Study sites: Wigwam Creek

Introduction

Methods

Results

Next Steps


Reach characteristics

• 14 reaches were selected over a range of drainage areas • All sites had mature spruce riparian forest • Length proportional to stream width (50x width)

Introduction

Methods

Results

Next Steps


Reach characteristics

• Length proportional to stream width (50x width) • Width ranged from 0.1 to 8.6m  • Length ranged from 30 to 250m 

Introduction

Methods

Results

Next Steps


Stream Measurements • Stream dimensions measured every 2x stream width • Local stream morphology and sediment size noted • Morphological influence of wood recorded

Introduction

Methods

Results

Next Steps


Woody debris survey

Introduction

Methods

Results

Next Steps


Stream Dimensions

Introduction Methods

Results

Next Steps


Downstream abundance of woody debris Small streams 1885 pieces of  wood were  surveyed.

Introduction Methods

Medium

Recruitment

Results

Larger

Recruitment + Transport

Next Steps


Downstream concentration of woody debris Small streams

Introduction Methods

Medium

Results

Larger

Next Steps


Downstream change in decay class

Introduction Methods

Results

Next Steps


Downstream change in position

Introduction Methods

Results

Next Steps


Proportion of wood in log jams

Introduction Methods

Results

Next Steps


Summary • Wood abundance may point to significant transport  beginning around 10km2 • Wood is predominantly fresh or very rotten upstream, and  transitions to moderate decay downstream • Wood gradually moves into “later stage” position classes • Jams appear downstream of 6km2

Introduction Methods

Results

Next Steps


Upcoming analyses • Analyze patterns of wood distribution • This will better identify wood jams (clusters) and  therefore, locations of wood transport

• Examine downstream changes in function and size classes • Compare time since death distributions  between sites using tree ring analysis of logs Introduction Methods

Results

Next Steps


Acknowledgements


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http://foothillsri.ca/sites/default/files/null/HLP_2009_12_Prsnttn_InfoSession_WheredoestheRiverTransportWoodLWD_Nicoll.pdf

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