Fluvial Geomorphology

Instream Forms

Module 8: Instream Forms

See Corresponding Assignment


Geomorphic units are the building blocks of riverscapes and the first step to reading riverscapes. In this unit, we focus on those building blocks that make up the channel. Geomorphic units are also a convenient lens for discriminating fluvial habitats. We looked at the Wheaton et al. (2015) Fluvial Taxonomy for geomorphic units, which is an extension and recasting of geomorphic units as described in your book and the River Styles Framework. The taxonomy also describes structural elements and margins in riverscapes, but that is not the focus of this unit.

Learning Outcomes

  1. Confidently read any riverscape and be able to map its core characteristics.
  2. Appreciate that topography is a quantitative record of landforms and apply morphometric analysis can be used to map and differentiate those landforms (i.e., geomorphic units).
  3. Gain an appreciation of how geomorphic processes of erosion, deposition transport and storage of sediment shape topography and create, maintain, sculpt and destroy distinctive landforms.

Lectures (videos) & Slides

Part 1 - Intro

Part 1 - Lecture Playlist

30 minutes

Part 2 - Book Description of Instream Geomorphic Units

Part 1 - Lecture Playlist

1 hour 5 minutes

Part 3 - Fluvial Taxonomy

Part 1 - Lecture Playlist

1 hour 10 minutes

See Wheaton et al. (2015) Fluvial Taxonomy resources below.

Exercises to Complete During Part 3 of Lecture

If you want to print out just the exercises you can do so below. Note we only use exercise 3, 4 and 5 (no need to print all 7 pages). These are from a capstone crash course in fluvial geomorphology:

Exercise Handout for Print

Other Resources

Field Trip Handout

On Monday, 3/15/2020 we visited the Logan River. For a PDF of handout, click below:

Field Trip Handout for Print
Share your Field Trip Photos Here!

Some Tips when Mapping in Field

  • Decide what tier of mapping is necessary for your purposes.
  • Clear definition of minimum mapping unit in terms of multiple of bankfull width (e.g. 0.25 bfw or 1/3 bfw) for minimum length-scale of longest axis of unit. This helps avoid mapping every micro-habitat (hydraulic unit scale) unit like pocket pools and focus on broader picture). We discussed how this choice is necessarily problem specific (e.g. you might go finer-scale for some fish habitat work; coarser-scale for broader geomorphic interpretations)
  • The fact that the taxonomy filters down your choices to 2 or 3 units at Tier 3 when applying one attribute at a time. The goal is not necessarily to get the absolute correct unit: but narrow down to possible candidates and sometimes units have a “complex” history and are truly a mix of different units. Sometimes it will obviously land on 1 unit, where it does not, don’t fight it or force it. Just say it is “one of these two or three”, or “most likely this one, but could be that one”, or “a mix of these two”.
  • Instead of focusing on identifying units by polygons and identifying their boundaries, when identifying in the field go to their defining point or mid point. For example, the top of a bar (convexity) , the deepest part of a pool (concavity), the crest of a riffle, the middle of a boring planar reach. Just identify the point and worry less about the boundaries between the units.

Map for Field Trip Reaches

Geomorphic Unit Toolkit

Corresponding Chapter in Course Text

From: Fryirs KA, Brierley GA. 2013. Geomorphic Analysis of River Systems: An Approach to Reading the Landscape, First Edition. Blackwell Publishing Ltd.: Chichester, U.K.

This module focus on: CHAPTER EIGHT: Instream geomorphic units

Relevant or Cited Literature

Follow up selected readings suggested by Fryris and Brierley (2013) are provided for every chapter in page 328-334 of the text book.

2015 Fluvial Taxonomy

Brierley & Fryirs (2005) River Styles Framework

The River Styles Framework is laid out in Part 2 of the Brierley and Fryirs (2005) book and is the conceptual basis for much of our book. For an overview lecture of the framework, see this Module in WATS 6860 Ecohydraulics.