Flooding in the Peace-Athabasca Delta

What is the PAD?

The Peace-Athabasca Delta (PAD) is a globally significant freshwater delta found in the northeast corner of Alberta. It is one of the largest freshwater delta ecosystems in the world. 

It is largely found within Wood Buffalo National Park—Canada’s largest national park and one of the largest protected areas in the world.

The delta is the traditional territory of a number of Indigenous peoples. Dene, Cree/Nehiyawak, and Metis peoples continue to live closely with the delta today. Its waters and meadows have provided rich hunting and harvesting areas for thousands of years and bore witness to the beginnings of the European fur trade in the late 1700’s.  

Deltas are created in areas where rivers slow down as they meet a larger body of water. This causes sand and sediment to fall to the river bottom. Over time, the built-up sediment causes the river to break from a single channel to a network of smaller, shallower channels. The PAD is a complex web of lakes and wetlands, grasslands and mixed forest which provides habitat for a wide range of plant and animal diversity. It is unique in Canada and the world and  is larger than many small countries on Earth.

The delta is many things at once. It has been protected as an integral part of Wood Buffalo National Park since 1926 when the park was expanded south of the Peace River. It also holds international recognition for its unique qualities.

The delta is considered a RAMSAR wetland of international importance because it supports an abundance of biodiversity, especially water birds and fish. For example, large colonies of gulls live in the delta during the summer, feeding on dense populations of minnows in delta lakes.

As a UNESCO site World Heritage Site, the PAD is internationally significant. The UNESCO World Heritage Centre declares that the PAD, with its great concentrations of migratory wildlife, is “ a rare and superlative natural phenomena, and a key element in WBNP’s World Heritage Site designation”. It is Parks Canada’s responsibility to protect the park in accordance with the Canada National Parks Act and its World Heritage Status.

To reinforce Parks Canada’s commitment to this protection, the park has developed the Wood Buffalo National Park Action plan after the concerns of Indigenous peoples over environmental stressors were brought forward. To learn more about the Action Plan, visit: 

Today’s Peace-Athabasca Delta is an important landscape for not only plants and wildlife, but for traditional Indigenous ways of life as well. The delta is most commonly accessed by boat or by canoe and in winter by over-snow vehicles or cars and trucks, using an ice road constructed by Parks Canada.

Flooding in the PAD

Flooding in the PAD is natural and necessary for it’s continued existence. While floods are generally considered dangerous and destructive events for people and property, places like the PAD are dependent on flooding.

The delta was created after the last ice age by meltwater streams from glaciers, snowfall and ancient lakes that covered the region. Over thousands of years, the wildlife, plants, people and ecosystems of the PAD have adapted to be resilient and reliant on floods.

The PAD’s mosaic of lakes and side channels are interconnected above and beneath the ground. They require high water levels for lakes and ponds to fill, flow and re-charge.

Peak water levels on the Peace and Athabasca rivers occur during spring break-up and in the summer following mountain snowmelt. In some years, rivers reach their highest levels when spring break-up coincides with ice jams. An ice jam event is when pieces of broken ice get pushed against each other and the jam event is when pieces of broken ice get pushed against each other and the river banks, causing water to build up behind it. A major ice jam can cause the flow in PAD channels to reverse. If the jam holds long enough, the backwater will overbank and overflow into surrounding marshes, meadows, side channels and oxbows.

With the high waters come nutrients in the form of silt and mud. Washed down from tributaries and streams, silt from as far as hundreds of kilometres away provides vegetation with the foundation to grow and flourish.

As vegetation such as willows and grasses abound, this helps aquatic wildlife such as muskrats and waterfowl benefit from improved habitat quality. Larger wildlife, such as the Bison, benefit from having quality habitat to range in and to forage.

The incoming water changes the environment by flooding meadows, submerging emergent vegetation, and inundating the roots of encroaching willows. Thus, floods maintain a variety of plant successional stages, contributing to the high biological productivity and diversity that characterizes the delta.

Breakup

Ice breakup occurs in early spring each year. As temperatures rise, snowmelt and rainfall increase flow into the watershed, raising water levels and increasing pressure on weakened ice. These conditions cause large segments of ice to break apart and flow down stream.

Over 400,000 square kilometres of watershed drain into the PAD through two of Canada's largest rivers: the Peace and Athabasca.   

These rivers collect snow melt, rain fall and glacial water from vast areas of northern BC, Alberta and Saskatchewan. 

Flowing past many rural communities, farmlands and industries- both rivers play integral roles in the lives of the territories and communities that they flow through.

The Peace River is approximately 1923km long, originating in BC in the Rocky Mountains and ending at the Slave River just north of the PAD in Alberta.

The Peace River watershed collects water from an area of approximately 250,000 square km across 2 provinces.

The Peace River and the PAD drains into the Slave River when water levels are low on the Peace River and higher in the PAD.

The Peace River drains into the PAD AND the Slave River when water levels are high on the Peace River.

The Athabasca River is approximately 1230km long, beginning at the Columbia Icefield in Jasper National Park and ending at the PAD.

The Athabasca watershed drains an area of approximately 160,000 square kilometres including 24% of Alberta's landmass and a portion of Saskatchewan.

The waters of Peace and Athabasca Rivers combine to create the lakes and channels of the delta at the western end of Lake Athabasca. Seasonal fluctuations such as wet or dry summers and years of higher or lower snowpack in the Rockies have immense impacts on how the flooding in the delta plays out. Waters in the delta gather and percolate through the marshes, draining north into the Slave River and eventually through the Mackenzie River in the NWT.

In the summer of 2020, a perfect storm of sustained higher than usual snowpacks, combined with a rainier than usual summer. This led to the high water levels not seen in many decades, and a number of perched basins in the delta receiving fresh water again.

2020 Athabasca River Breakup

2020 Peace River Breakup

2020 Flood

Although ice jam floods occurred in 2014 and 2018, in the spring of 2020, the Peace-Athabasca delta region (PAD) of Wood Buffalo National Park experienced its most significant flood event in many years, with water levels occurring that had not been seen since the floods of 1996-1997.

In light of the possibility of significant flooding in the delta, Parks Canada convened a multi-agency team of operational staff from Alberta Environment and Parks, ECCC, BC Hydro and the Indigenous-led Community-Based Monitoring Programs. This operational team was brought together to actively share information regarding monitoring, ice break-up and flood forecasting programs on the Peace, Slave and Athabasca rivers. The team was also formed to help, coordinate both monitoring and incident response during the spring breakup in the PAD. These partners coordinated real-time monitoring efforts (including aerial observations, water level gauge readings, ice thickness measurements and remote cameras) and shared information on their programs. This collaboration helped to provide public safety alerts and advisories for visitors and traditional land-users who normally work and live in the PAD.

Timelapse of satellite camera images taken at Peace Point during 2020 breakup

In addition to the real-time flood monitoring, satellite imagery was acquired to document the extend of high waters throughout the PAD. Extensive imagery was acquired between April 28 and May 30 with a focus on the week of May 3 to May 10. With this satellite imagery and the use of real-time monitoring data, this flood extent was compared to other yearly estimates of flood extent from 1996 to 2020. 

Sentinel Imagery 2017 (left) vs 2020 (right)

A short ice jam (approximately 7.5 km long) also formed downstream of the junction of the Peace, Slave, and Des Rochers Rivers on May 6. This jam was so huge, that a portion of the incoming ice was diverted from the Peace River; backwards down the channel of the Rivière Des Rochers and into Lake Athabasca. However, as this ice jam was short lived and not more persistent , limited high water levels and overbank flow magnitude was not more significant. In this respect, the 2020 flood event was different from previous historic flooding events. (e.g. 1974, 1996, 1997 and 2014). In these earlier events, unlike in 2020, PAD flooding was driven largely by major ice-jamming in the lower Peace - upper Slave River reach, which typically results in the replenishment of perched basins in the Peace section of the PAD. Though such overbank flooding was limited in 2020, the flow magnitude was high enough to cause flow reversals in the connecting channels which likely contributing to flooding of central-delta lakes and adjacent basins.

The results from the preliminary analysis of this imagery and data suggests that the spring 2020 flood was indeed, the most extensive since the spring floods of 1996 and 1997. Flooding appears to have been most extensive within the Athabasca River portion of the Delta, the central delta lakes and adjacent perched basins. 

Satellite imagery dating back to 1984 has been used to measure the amount of open water in the PAD.

This event provides a striking example of the delta’s amazing range of conditions, illustrating the possibility of wet or dry extremes on an annual basis while the long term trend toward drier conditions prevails. Indeed, relatively wet summer conditions and high summer flows on both the Peace and Athabasca Rivers have sustained exceptionally high water levels in the delta through to the start of the freeze-up period in fall 2020.

Historic High Water Levels in the PAD

Many areas of the PAD saw significant and prolonged periods of high water throughout the summer of 2020. Some Indigenous Knowledge holders describe water levels in the delta as the highest ever seen, indicating that we have witnessed a spring-to-summer flood season that only occurs once in a generation/once in a lifetime. Using the map below, you can explore some aerial photos of these areas.


Documenting and showcasing the timeline of the floods and monitoring of them was a widespread effort of many partners, all the members of the Wood Buffalo National Park Action Plan, and the Environmental Flows and Hydrology Working Group which included:

  • Alberta Environment and Parks River Forecast Centre
  • BC Hydro
  • Environment & Climate Change Canada
  • Mikisew Cree, Athabasca Chipewyan, Little Red River Cree First Nations and the Fort Chipewyan Metis Council
  • Members and volunteers from the Fort Chipewyan community based monitoring program

Photos

Generously supplied by Alberta Environment and Parks, BC Hydro, Environment Canada and Climate Change, and Parks Canada staff 

Satellite imagery of Smoky River

Credit: European Union, contains modified Copernicus Sentinel data 2021 processed with EO browser 

Break-up section 

Map data contains information licensed under the Open Government Licence ( Alberta), Open Government License (Canada), and Open Government License (British Columbia)

Sentinel Imagery 2017 (left) vs 2020 (right)