7. Topographic Changes

Module 7 - Topographic Changes

The Set-Up

The River Feshie, Scotland, UK

We will take you to the Highlands of Scotland, to the River Feshie to help you become familiar with quantitative analysis of channel geometry changes (the subject of Chapter 6). In the figure at right from Wheaton et al. (2013) we can see a braided gravel bed river actively adjusting through time. You will be given access to topographic surveys from 2003, 2004, 2005, 2006 and 2007 of this reach.

In the book, your authors talk about bed and bank processes that influence channel shape. You will zoom in and look directly at such changes to a real river, and use a tool, the Geomorphic Change Detection Software to analyze it quantitively.

Purpose

The goals of this assignment is to i) give you experience working with topographic datasets (that capture channel geometry), and ii) help you recognize and identify specific mechanisms of geomorphic change from repeat topographic datasets. These concepts were cast in Chapter 7 as "Channel Geomery" changes and here we will unpack that a little more with topographic analysis.

Prerequisites

Students/Participants are expected to have some previous GIS experience, familiarity with ArcGIS (don’t need to be an expert), and some understanding of topographic data and digital elevation models.

The Assignment

Part 1 - Get Ready For Monday - Build Project & Do Some Budget Segregation

For the first part of this assignment, I want you to do:

1.A Download the Feshie Data (also below)
1. B Create a GCD Project (you will bring this to class on Monday and turn this in for Part 2) with at least:
- 1.B.1: Three of the Five years loaded as surveys (see videos for how to do error modelling)
- 1.B.2: Two change detections (threshold @ 80% probability) for two of the epochs
- 1.B.3: A budget segregation with at least two examples each of the following mechanisms of change identified:
  - Bank Erosion
  - Channel Bed Lowering (degradation / incision)
  - Channel Bed Rising (aggradation)
  - Bar Development

Come to class with your GCD project handy to show, and your list of questions and/or problems you encountered. You will work on small groups and share your projects, and explain what you found.

Concepts to Illustrate & Explain

Building your GCD Project. In this tutorial, I show you how to get through 1.B.1 and 1.B.2 above.

Doing Budget Segregation. In this tutorial, I show you how to get through 1.B.3 above.

For more information on budget segregation, see the following GCD Tutorials:

Part 2 - Turn in a Web Page

You will prepare a web page explaining what you did and defending your interpretations. Please include clear annotated figure(s) and/or video showing the identification two examples each of these four mechanisms:

Bank Erosion
Channel Bed Lowering (degradation / incision)
Channel Bed Rising (aggradation)
Bar Development

If you opt not to use video, please instead describe with text what you interpreted and justify your interpretation.

Resources

Dataset

River Feshie, Scotland, UK

A 700 m long braided reach. Dataset.

Datset includes:

700m braided gravel bed river in the Scottish Cairngorm mountains
5 annual surveys
Mix of RTKGPS and Total Station
1m cell resolution

Relevant Paper

The work we will do on "budget segregation" is based on Wheaton et al. (2013):

Wheaton JM, Brasington J, Darby SE, Sear DA, Vericat D‡., and Kasprak A. 2013. Morphodynamic signatures of braiding mechanisms as expressed through change in sediment storage in a gravel-bed river. Journal of Geophysical Research - Earth Surface. DOI: 10.1002/jgrf.20060.

Album

Here is a Google Album of the Feshie to get a better feel for the site.

More Background on GCD

We have taught numerous courses and workshops on GCD. The following resources might be helpful if you want a deeper treatment of the methods and topics: