Questions and Answers
What is the current paradigm of stream restoration?
Create a stable, single thread, meandering channel.
Which of these are common elements in most stream restoration projects? (Select all that apply)
What does stability of a stream entail?
Channel does not move; channel does not erode banks.
What are some problems with the current paradigm of stream restoration? (Select all that apply)
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What is the utility of a meandering channel?
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What is the origin of the stable, single-thread, meandering channel?
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What is the basic principle of Rosgen Stream Classification?
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Which features are associated with a Rosgen stream? (Select all that apply)
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How does the Rosgen classification system function?
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What does stream classification level 1 involve?
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Match the stream types A to G with their characteristics:
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What does stream classification: level II cover?
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What does a lower entrenchment ratio signify?
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What is the significance of bed material/substrate?
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How is sinuosity calculated?
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What does stream classification: level III assess?
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What is a utility of the Rosgen approach?
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What happened in the case study of Cuneo Creek, CA?
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What was the outcome of the Uvas Creek, CA project?
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What is problematic about using channel form as the entire basis for reconstruction?
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What is required to predict bank failure accurately?
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What limitations do projects face regarding spatial and temporal scale?
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What is a key issue with sediment systems during restoration?
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Study Notes
Current Paradigm of Stream Restoration
- Emphasizes the creation of a stable, single-thread, meandering channel.
Common Elements in Stream Restoration
- Aims for a "natural looking" channel.
- Integrates ecology and geomorphology with engineering principles.
- Incorporates self-sustaining designs that align with natural processes.
Stability of a Stream
- A stable channel remains in place without significant movement or erosion of banks.
Problems with Current Restoration Paradigm
- Certain channels may not naturally meander.
- High sediment supply can hinder lane equilibrium.
- Limited funding for post-completion assessments.
- Fails to consider stream connectivity.
- Geomorphology often overlooked in Rosgen approach.
Utility of a Meandering Channel
- Designed to efficiently transport water without significant erosion or accumulation of sediments.
Historical Origin of Channel Design
- Concept of stable, single-thread channels originates from British irrigation channels in India.
Rosgen Stream Classification Principles
- Predicts stream behavior based on physical appearance.
Characteristics of Rosgen Streams
- Features a meandering form with rooted vegetation on outer banks to prevent erosion.
- Contains boulders that create riffles and pools, enhancing stream roughness.
Functionality of Rosgen Classification System
- Classifies streams to predict stability and provides guidelines for constructing stable channels.
Stream Classification - Level 1
- Involves geomorphic characterization using topographical maps and aerial photos.
- Key factors include channel slope, shape, and patterns, yielding classifications from A to G.
General Trends in Stream Types
- A streams: Incised in valleys with high sediment supply.
- B streams: Moderately incised, wide and shallow, known as "babbling brooks."
- C streams: Not incised, wide, shallow, and found in alluvial valleys; the most common type.
- D streams: Exhibit multiple channels, remaining wide and shallow with low slopes.
Stream Classification - Level II
- Details morphological descriptions including width/depth ratio, entrenchment ratio, sinuosity, channel slope, and materials.
Entrenchment Ratio Explained
- A lower entrenchment ratio indicates a more entrenched (incised) channel.
Bed Material/Substrate Analysis
- Use pebble counts to assess bed materials across the channel, focusing on the average intermediate axis.
Sinuosity Calculation
- Defined as actual channel length divided by straight valley length.
Stream Classification - Level III
- Evaluates stream "state" including bank erosion potential, riparian vegetation, and sediment supply.
Utility of Rosgen Approach
- Facilitates quick classification of various channels with minimal technical expertise.
Case Study: Cuneo Creek, CA
- C3 stream aimed to transform a braided channel into a single-thread channel but failed due to upstream sediment supply issues.
Case Study: Uvas Creek, CA
- Sought to restore a C4 channel in an urban drainage basin but experienced catastrophic failure due to unexpected flooding and lack of evidence supporting the restoration plan.
Issues with Channel Form Misuse
- Relying solely on channel form neglects important factors such as spatial, temporal scales, and geomorphic conditions.
Channel Form Misuse: Bank Failure
- Requires measurements of shear stress and pore water pressure to predict bank stability, which are inadequately addressed in the Rosgen method.
Channel Form Misuse: Scale Limitations
- Projects often lack sufficient funding for long-term monitoring post-construction.
Channel Form Misuse: Sediment System Considerations
- Failure to account for sediment dynamics entering or exiting the system and legacy sediments can lead to ineffective stream restoration.
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Description
Explore key concepts in stream restoration through this quiz. Understand the current paradigms and essential elements that make up successful restoration projects. This will help reinforce your knowledge of ecological and geomorphological integration in stream management.