Stream Restoration Concepts

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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)

Designed for high energy flow

Integrate ecology and geomorphology with engineering (correct)

Natural looking channel (correct)

Work with natural processes (self-sustaining design) (correct)

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)

Some channels won't want to meander Signup and view all the answers

What is the utility of a meandering channel?

Built to move water efficiently without eroding or being built up. Signup and view all the answers

What is the origin of the stable, single-thread, meandering channel?

British irrigation channels in India. Signup and view all the answers

What is the basic principle of Rosgen Stream Classification?

Predicting stream behavior from appearance. Signup and view all the answers

Which features are associated with a Rosgen stream? (Select all that apply)

Presence of boulders creating riffles and pools Signup and view all the answers

How does the Rosgen classification system function?

It predicts a stable channel for the system and provides a recipe on how to build a stable stream. Signup and view all the answers

What does stream classification level 1 involve?

Geomorphic characterization using top maps/air photos. Signup and view all the answers

Match the stream types A to G with their characteristics:

A Stream = Up in the valley, incised, high sediment supply B Stream = Moderately incised, wide and shallow, moderate slope C Stream = Not incised, wide and shallow, low slope, alluvial valley D Stream = Multiple channels, wide and shallow, low slope Signup and view all the answers

What does stream classification: level II cover?

Stream types 1-6: morphological descriptions including width/depth ratio and channel slope. Signup and view all the answers

What does a lower entrenchment ratio signify?

More entrenched channel (more incised). Signup and view all the answers

What is the significance of bed material/substrate?

Can use pebble count measurements across the channel. Signup and view all the answers

How is sinuosity calculated?

Actual channel length / straight valley length. Signup and view all the answers

What does stream classification: level III assess?

Stream 'state' or 'condition' including bank erosion potential and riparian vegetation. Signup and view all the answers

What is a utility of the Rosgen approach?

Can classify channels quickly without deep understanding. Signup and view all the answers

What happened in the case study of Cuneo Creek, CA?

The channel plan failed due to high sediment load from upstream logging. Signup and view all the answers

What was the outcome of the Uvas Creek, CA project?

The channel retired to a braided channel after catastrophic failure from a single flood. Signup and view all the answers

What is problematic about using channel form as the entire basis for reconstruction?

Does not take into consideration spatial and temporal scale and geomorphic conditions. Signup and view all the answers

What is required to predict bank failure accurately?

Measurements of shear stress, pore water pressure, etc. Signup and view all the answers

What limitations do projects face regarding spatial and temporal scale?

Limited to construction duration and no funds allocated for future monitoring. Signup and view all the answers

What is a key issue with sediment systems during restoration?

Not accounting for sediment entering/exiting the system. Signup and view all the answers

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.