DESCRIBING DAMAGE TO STREAM MODIFICATION PROJECTS

ABSTRACT

Complex relationships between stream functions and naturally stochastic processes make evaluation of stream modification projects difficult. Informed by vague objectives and little monitoring data, project evaluations can often be a subjective attribution of success or failure. Given that channel form is closely related to stream function, this research provides a framework to rapidly assess current conditions as a continuum of damage to channel functioning. The damage states focus on damage to hydraulic and geomorphic parameters that describe basic stream functioning and support higher level functions including managing water quality and supporting various life cycles. Based on widely accepted evaluations of physical habitat quality and stream stability, the damage states describe a continuum of damage in multiple categories related to the stream functions that are affected by the modification design. The highest level of damage in the damage categories provides an overall assessment of project conditions and the individual scores in the damage categories can be used to calculate relative vulnerability and relative risk associated with the stream modification project. Relative risk is determined using a vulnerability-criticality risk logic matrix which provides a category of recommended action based on project conditions and potential impacts. The damage states provide an objective characterization of post-construction project performance and the risk assessment provides guidance for allocating resources to project maintenance or rehabilitation. These tools can be used to improve the results of stream modification and protect environmental resources and physical

assets.

 

TABLE OF CONTENTS

List of Figures ………………………………………………………………………………………………………….. vi

List of Tables …………………………………………………………………………………………………………… viii

Acknowledgements …………………………………………………………………………………………………… x

Chapter 1  Introduction ……………………………………………………………………………………………… 1

Chapter 2  Literature Review ……………………………………………………………………………………… 3

2.1 – Introduction ………………………………………………………………………………………………. 4

2.1.1 – Stream Modification Terminology and Common Practices ……………………. 5

2.1.2 – Functions and Services in Modified Stream Channels …………………………… 9

2.1.3 – Goals, Objectives, and Performance Standards …………………………………….. 10

2.1.4 – Increasing Stream Function through Stream Modification …………………….. 14

2.2 – Current Measures for Success and Failure …………………………………………………….. 18

2.2.1 – Determining Failure of Stream Modification Projects …………………………… 20

2.2.2 – Failure Modes of Structures ………………………………………………………………. 21

2.2.3 – Application of Damage States to Complex Systems ……………………………… 24

2.3 – Methods for Assessing Risk in Modified Streams ………………………………………….. 27

2.3.1 – Failure Modes and Effects Analysis ……………………………………………………. 28

2.3.2 – Fault Tree Analysis and Cut Sets ……………………………………………………….. 30

2.3.3 – Risk Matrices…………………………………………………………………………………… 32

2.4 – References ………………………………………………………………………………………………… 35

Chapter 3  Describing Damage to Stream Modification Projects …………………………………….. 43

3.1 – Levels of Achievement ………………………………………………………………………………. 44

3.2 – Damage States …………………………………………………………………………………………… 48

3.2.1 – Damage States for Improved Projects …………………………………………………. 50

3.2.2 – Damage States for Enhanced Projects …………………………………………………. 57

3.2.3 – Damage States Discussion…………………………………………………………………. 65

3.3 – Vulnerability-Based Risk Assessment ………………………………………………………….. 67

3.3.1 – Vulnerability……………………………………………………………………………………. 673.3.2 – Criticality ………………………………………………………………………………………… 72

3.3.3 – Relative Risk …………………………………………………………………………………… 85

3.4 – References ………………………………………………………………………………………………… 88

Chapter 4  Case Studies …………………………………………………………………………………………….. 90

4.1 – Case Study 1: Roaring Run at State Route 445 ………………………………………………. 91

4.1.1 – Damage to the Roaring Run Case Study ……………………………………………… 934.1.2 – Risk of the Roaring Run Case Study …………………………………………………… 99

4.1.3 – Discussion of the Roaring Run Case Study ………………………………………….. 101

4.2 – Case Study 2: Bald Eagle Creek at Port Matilda ……………………………………………. 102

4.2.1 – Damage to the Bald Eagle Creek Case Study ………………………………………. 104

4.2.2 – Risk of the Bald Eagle Creek Case Study ……………………………………………. 115

4.2.3 – Discussion of the Bald Eagle Creek Case Study …………………………………… 118

4.3 – Case Study 3: Spring Creek at Bellefonte ……………………………………………………… 119

4.3.1 – Damage to the Spring Creek Case Study …………………………………………….. 121

4.3.2 – Risk of the Spring Creek Case Study ………………………………………………….. 132

4.3.3 – Discussion of the Spring Creek Case Study …………………………………………. 134

4.4 – References ………………………………………………………………………………………………… 136

Chapter 5  Conclusions ……………………………………………………………………………………………… 138

Appendix A  Stream Modification Practices ………………………………………………………………… 142

Appendix B  Images and Photographs of Case Studies ………………………………………………….. 145

Chapter 1

 

Introduction

The evaluation of stream modification projects is made difficult by the stochastic processes and intricately connected functions that govern the physical form of a stream. Failure is an ambiguous descriptor for these projects but damage to natural stream functions can be discussed in more concrete terms.  In order to determine success or failure of stream modification projects, evaluation criteria must be tailored to the unique ecological and social goals of each project. However, resources for both monitoring and evaluation are scarce and project evaluation can be subjectively based on a combination of ecological, political, or social criteria. An alternative to declaring project failure following a hydrologic event is to define states of damage to hydraulic and geomorphic channel functions. Channel form is closely related to stream function and damage states can be used to rapidly assess damage to channel functioning.

Numerous studies have shown that urbanization or agricultural development can degrade stream ecosystems and result in a decrease of stream functioning. Activities that degrade stream functioning may not be reversible. Additionally, the ability to restore channels may be constrained by physical changes in the urban environment, such as infrastructure and property boundaries. The objective of this research was to develop a tool to describe damage to stream modification projects that:

• are based on natural channel functioning;
• account for both environmental goals and human-made constraints; and
• are widely applicable in urban settings.

 

The realization of these objectives is semi-quantitative damage states defined for hydraulic and geomorphic functioning of modified channels in urban or otherwise constrained settings. Stream modification projects intentionally change physical characteristics of the channel and therefore alter how water, debris, and sediment are transported in the modified channel. These hydraulic and geomorphic functions affected by modification govern the equilibrium state of the channel and are connected to higher chemical and biological stream functioning. While quantifying hydraulic and geomorphic functioning would be subject to large variations across regions and streams, the damage states are based on semi-quantitative assessment tools for widely recognized symptoms of damage, such as degradation, excessive sediment deposition or bank erosion.

In addition to evaluating damage, the damage states can be used to describe the vulnerability of modified channels in a semi-quantitative risk assessment procedure based on the current conditions of a project. The dynamic and stochastic nature of riverine ecosystems creates considerable uncertainty in predicting system responses to modification which results in risk to the environment and infrastructure. A vulnerability-criticality risk-logic matrix is proposed that can be used to determine relative risk of multiple stream modification projects with similar goals. This research proposes a novel framework for assessing damage and evaluating relative risk of

stream modification projects.

DESCRIBING DAMAGE TO STREAM MODIFICATION PROJECTS

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