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The Bog is where thoughts, opinions, discussion pieces, and action converge. Influential thinkers from the water community are invited to share their insights on current or controversial water topics. Please note that the views expressed herein are those of the authors, and do not necessarily reflect the position of the Alberta WaterPortal.
Rewilding Our Rivers: The Floodplain – The River’s Room to Breathe by Lauren Eden
Welcome back to the Rewilding Our Rivers Discussion Series. Today we will look at the role of the floodplain and the importance of designing systems that support the meandering wishes of our rivers.
A floodplain is the flat area of land along a river or stream that is subject to flooding. The width of the floodplain is dependent on the meandering amplitude of the river. It is essentially the breathing room for a river or a stream to meander, overflow, re-route and change course. Rivers will flow where they want and the floodplain is there to provide space for the river to move.
The ecosystem of the floodplain consists of native grasses, woodlands, wetlands and riparian zones. The establishment of rooted vegetation helps to absorb the force as well as the volume of rising floodwaters. The vegetation also serves to stabilize bank erosion, filter pollutants and provide habitat for animals and recreational spaces for humans. Development of impervious surfaces on the floodplain such as buildings, roads and parking lots hinder the ability of the floodplain to absorb floodwaters and at the same time speeds up runoff into streams leading to increased downstream flooding.
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Rewilding Our Rivers: The Riparian Edge by Lauren Eden
So far in the Rewilding our Rivers Discussion Series, we have discovered the importance of healthy soil systems and wetlands in the attenuation of water during flooding events. The previous two blogs talked about how soils rich in organic matter hold and retain more water, and how wetlands function like sponges across the landscape absorbing surface water runoff subsequently replenishing aquifers. In addition to ensuring that Alberta’s soils and wetlands are healthy, riparian zones also play a beneficial role in flood mitigation.
The riparian edge is where aquatic and terrestrial ecologies interface; formed by the merging of land and a river, lake, or stream. As unique ecosystems, riparian zones provide a vast array of ecological goods and services including decreased soil erosion; storing and recycling of organic matter; providing habitat for fish and wildlife; and improving water quality through the removal of nutrients such as nitrogen and phosphorus from surface and subsurface water. The functioning of these many goods and services is highly dependent on the width of riparian vegetation; at minimum a riparian zone should extend over the stream bank and 5 to 10 metres onto the floodplain.
Rewilding Our Rivers: Wetlands – Nature’s Kidneys by Lauren Eden
Last week we learned the value of healthy soils and their role in flood mitigation . This week in honour of World Wetland Day 2014 on February 2, the Rewilding Our Rivers Discussion Series will turn its attention to the significance of wetlands and their potential role in flood mitigation.
Wetlands are often called planet earth’s kidneys because of their ability to purify our water supply through natural filtration systems that absorb heavy metals and other harmful containments (like phosphorus). Wetlands are complex ecologies that offer many benefits and functions to our shared bio systems - most notably, they are able to retain and store water. In essence, wetlands act like sponges; they absorb rainfall, slowly saturate soil systems, and eventually recharge aquifers. By retaining and storing water, wetlands reduce the speed and volume of water entering our streams and rivers. This can be particularly important for some flood events.
|"Wetlands near Utikuma Lake, northern Alberta 2010" by Gord McKenna is licenced under CC BY 2.0.|
The Ramsar Convention defines wetlands as areas of marshes, bogs, fens and peatlands. They are ecosystems that contain plant and animal life in water saturated areas. A wetlands’ ability to retain and store water is greatly dependent on its soil system. For instance, peatlands have a significantly greater capacity to retain and store water because they are made up of rich organic matter developed over thousands of years. This highlights the symbiotic relationship between wetlands and healthy soil systems and the role they can play in flood mitigation. Peatlands have become important ecosystems to protect on a global scale due to the simple fact that they are nearly impossible to reconstruct. One example of this is located in our back yard. Alberta is home to a UNESCO World Heritage Site and a Ramsar Convention Wetland of international importance located in the Peace-Athabasca Delta in the Wood Buffalo National Park.
What is Old is New Again: Elbow River Historical Detention and Diversion Sites Report
A new report on historically identified detention and diversion sites, commissioned by the Alberta Flood Recovery Task Force and executed by Alberta WaterSMART, has been added to the Flood Recovery Task Force page.
This report explores 100-110 years of historical documentation on previously considered options for both drought and flood mitigation in the Elbow River Watershed. Many of the potential options come from reports by the Department of the Interior (established in 1873 by Sir John A. MacDonald) which had surveyed the land by foot looking for sites where the topography of Alberta could be used to create reservoirs to combat drought.
The purpose of this study is to review historical records to identify previously proposed detention and diversion sites on the Elbow River, and determine if these historical sites have any merit for further investigation and consideration by the Government of Alberta (GoA) as an alternative to the mitigation options currently being reviewed by the Flood Recovery Task Force.
An initial historical review of potential detention and diversion sites on the Elbow River provided twelve possible options that could be implemented to mitigate for both flood and drought.
Of the twelve identified historical detention and diversion sites it is recommended that the Priddis Creek diversion be seriously considered as an option for flood and drought mitigation. The Priddis Creek diversion is designed to mitigate for flooding upstream of Bragg Creek and the City of Calgary using the natural creek bed and low lying topographical areas for channeling the water flows. By using natural topography the Priddis Creek diversion has a greater potential to slow down the water; subsequently reducing peak flows. It is also recommended that the historical resevoir sites identifed by the Department of Interior in the 1890s, along with the McLean Site, should be further investigated for feasibility. These storage sites are recommended due to their use of natural topography and their ability to mitigate for flooding upstream of Bragg Creek and the City of Calgary.
In order to ensure that all the flood mitigation options are considered for all watersheds throughout Alberta, Alberta WaterSMART recommends further investigation into all mitigation options by continuing to undertake this type of historical analysis for all watersheds throughout Alberta.
Some of the current proposed options have received criticism by the water community for the potential impact they would have on the watershed. Do any of these proposed options seem like promising alternatives? If not, what options would you recommend exploring?