Editor’s Note: This post on river lessons by the Wild Trout Trust was written by Steve Grimmer, Little River’s Artist Mechanic.
On our Youtube channel we have a playlist called Emriver in Action that’s full of cool videos of our models out in the world helping folks teach and research about fluvial geomorphology.
One great organization, the Wild Trout Trust, has a series of four short videos they made during the CLA Gamefair in 2013 with an Emriver Em2 stream table lent by the equally terrific Severn Rivers Trust.
The Wild Trout Trust is not an angling organization, but a conservation group that has as its mission to improve trout habitat in the UK and Ireland. They do this through education and consulting on river rejuvenation projects. To quote them:
Our approach to habitat and ecosystems is based on science and refined by experience of the practical application of habitat improvements.
This is a group after our own hearts at Little River! Not only is it great to see our stream tables out on the job so to speak, but it is especially gratifying to hear and see river processes explained so clearly and knowledgeably, with direct illustrations both in the model and in the field.
If you have an Emriver stream table or are curious as to how they might help you teach about fluvial geomorphology and river conservation, these four videos could be a great help to you.
Emriver Introduction: erosion and deposition in a self-forming model river channel
This video is a two-minute introduction to an Emriver Em2 stream table with color-coded plastic media. The narrator mentions self-determination of channels for specific box slopes and water flows based on erosion and transport of sediment, and deposition of particles based on size and flow rates. He also points out how faster flows scour down into smaller sediment sizes.
In the second half, the narrator shows how installed materials such as vegetation and flow-deflectors scale from the field to the model and demonstrate bank armoring and scour pools.
Unintended effects of dredging
This video is another introduction to an Em2 stream table. The narrator begins by showing headcut erosion in the form of a nick cut progressing upstream in an effort to rebalance streambed gradient. He then shows how steambed removal increases the rate of erosion and sediment transport both up and downstream from the removal point.
The second demonstration explains how attempts to increase a channel’s carrying capacity beyond its natural dimensions by dredging cause an increased demand for sediment from upstream resulting in increased erosion and filling in of the dredge site.
Rebalancing bank erosion rates
This video is a three-minute demonstration of the ways an Em2 stream table with color-coded media can help visualize differential particle size erosion and deposition, along with strategies for successful stream bank armoring. The narrator shows several examples of collapsing riverbanks in the field along with attempts at bank control with stone and brushy vegetation.
He demonstrates how stone bank armoring can increase water velocity and cause more erosion of nearby soft banks, which often leads to failure of the stone wall. As an alternative, the narrator uses modeled vegetation along a river bank in the Em2 stream table to slow the water flow and encourage sediment buildup, allowing the river to naturally rebuild itself. Several real-world examples are shown of the modeled phenomena, reinforcing the message.
Weirs and impacts on river life
This four-minute video demonstrates how an Em2 stream table can help the public understand the characteristics of a river with a variety of habitats and how weirs can often be detrimental to natural river processes and wildlife. The narrator describes how a river’s flow rate, depth, and bed material all contribute to creation of a specific blend of river habitats and channel features.
He shows how a weir pond is unable to produce varied conditions conducive to a healthy wildlife population, and how the increased velocity and sediment starvation of water below a weir cause excessive erosion and bank degradation.
The narrator then uses the Em2 to demonstrate how a weir upsets the balance of sediment supply and deposition in a river. He shows increased deposition upstream of the weir leading to in-filling of a pool, and scouring of sediment immediately downstream along with decreased natural gravel bar and meander formation. He also describes how this sediment-starved section of the river is less resilient to flood events.
Thanks to Wild Trout Trust and Severn Rivers Trust for all you both do for river conservation and education.