Flood Mitigation: Understanding Groundwater Flooding
What is groundwater flooding?
In the event of heavy rainfall, underground aquifers (areas with permeable rock that water can pass through) are inundated and filled, possibly resulting in flooding [i]. “Groundwater flooding” is the flooding caused by water travelling through the ground, not over the land. In a flood, distinguishing between the two can be difficult or even impossible, but the difference can be important for considerations such as insurance claims [ii] and mitigation techniques [iii]. The damage to property and infrastructure caused by groundwater flooding can be extensive and detrimental to the integrity of buildings.
How does this option help to mitigate the impacts of a flood?
Groundwater flooding can result in damage to basements, due to underground water tables rising above minimum basement grades and further entering buildings through seepage and cracks in foundation. Another common source of flooding is through sewer pipes, which fill up and push water and sewage into basements [iv]. Monitoring and managing this source of flood water is important to mitigate the impacts of a flood.
Modelling groundwater flooding and mapping areas at risk of groundwater flooding are important mitigation methods to determine potential impacts and subsequent responses to flooding. Having this technology and ability to monitor groundwater levels is important for managing water and responding to flood events [v].
What understanding of groundwater flooding is already in place in Canada?
At present, Canada does not have extensive groundwater monitoring, mapping, or modelling technology that identifies high groundwater flood-risk areas. Improving groundwater management and knowledge will be important for future flood preparedness and mitigation measures.
What level of government is responsible?
Provincial and territorial governments are responsible for groundwater management and regulations associated with groundwater in their jurisdictions. In Alberta, the Water Act prescribes licenses, while the Environmental Protection and Enhancement Act ensures that groundwater quality is maintained and protected [vi]. From a policy perspective, the Water for Life Strategy, Water Management Plans, Land-Use Framework, and Water Conservation and Allocation for Oilfield Injection all address groundwater and the need to protect this important resource. Research and decision-making on groundwater will continue to be important for understanding flooding and other areas, such as coalbed methane development.
Does this policy account for differences between jurisdictions?
Understanding the role groundwater plays in overall watershed health and water systems may require specific jurisdictions to be considered before understanding the larger picture. In Alberta, the Land-Use Framework attempts to establish this understanding by initiating groundwater management through the development of a series of Groundwater Management Frameworks [vii]; however, this work has yet to be completed.
What is the scale and boundary of this policy?
Policies and legislation addressing groundwater resources in Alberta apply at the provincial level. Research on groundwater, however, is done at the regional level, where specific information can be gained. Alberta groundwater research and policies apply only in Alberta, but there is transboundary cooperation with the province’s neighbours.
What are the enforcement measures?
Specific enforcement measures related to groundwater do not currently exist in Alberta; however, directives protect groundwater resources, especially in the process of energy extraction. For example, the Alberta Energy Regulator has released numerous groundwater-related directives aimed at coalbed methane production to protect groundwater resources. These include: Directive 009, which requires cement casing; Directive 035, which requires baseline water well testing; Directive 044, which requires surveillance, sampling, and analysis of water production; and Directive 083, which addresses hydraulic fracturing operations.
Other jurisdictions may have regulations more focused on residential sewer flooding from groundwater, such as Wessex Water in the UK [viii].
What are the effects on the surrounding environment and watershed?
Groundwater plays an important role in overall watershed and ecosystem health; therefore, understanding this valuable resource is integral to determining what role aquifers play in flooding and water supply. This interconnection between surface water and groundwater flooding [ix] in any area requires research to determine environmental and watershed impacts.
Would understanding groundwater help in a drought?
Yes, having a greater understanding of the connection between groundwater and surface water would help us to manage drought conditions. Groundwater is important to drought management because it can provide an alternative source of water, indicate drought conditions due to lower water levels in lakes and rivers, and determine impacts on water quality that can also harm aquatic species [x].
An innovative approach to managing flood waters is to divert floodwater into the aquifers and so reduce surface water flooding. In principle, floodwater is diverted into seepage areas [xi] or forcibly pumped into aquifers to provide flood protection and to recharge the aquifer for later use [xii].
Sources:
[i] Environment Agency, 2019, What is groundwater flooding? https://environmentagency.blog.gov.uk/2019/12/23/what-is-groundwater-flooding/. Accessed 2023-05-05.
[ii] Insurance Bureau of Canada, 2017, A Guide to Residential Water Damage and Flood Insurance. http://assets.ibc.ca/Documents/Brochures/A-Guide-to-Residential-Water-Damage-and-Flood-Insurance.pdf. Accessed 2023-05-05.
[iii] City of Calgary, n.d., Groundwater 101 – The City of Calgary’s Flood Mitigation Strategy. https://www.youtube.com/watch?v=OvvWbPiWU34&ab_channel=CityofCalgary. Accessed 2023-05-05.
[iv] Abboud, J. & Ryan, C., 2017, Groundwater Flooding in a River-Connected Alluvial Aquifer. https://www.researchgate.net/publication/321817513_Groundwater_Flooding_in_a_River-Connected_Alluvial_Aquifer. Accessed 2023-05-08.
[v] University of Calgary, 2018, Groundwater flooding, not sewer backup, blamed for damaging homes along Elbow River in 2013. https://ucalgary.ca/news/groundwater-flooding-not-sewer-backup-blamed-damaging-homes-along-elbow-river-2013. Accessed 2023-05-05.
[vi] Government of Alberta, 2023, Water legislation and guidelines. https://www.alberta.ca/water-legislation-and-guidelines.aspx. Accessed 2023-05-08.
[vii] Government of Alberta, 2023, Groundwater – Management. https://www.alberta.ca/groundwater-management.aspx. Accessed 2023-05-08.
[viii] Wessex Water, 2018, How groundwater causes sewer flooding. https://www.youtube.com/watch?v=7b4uaY4H1Tk&t=3s&ab_channel=WessexWater. Accessed 2023-05-08.
[ix] https://www.youtube.com/watch?v=cC4LNxlmYPM. Accessed 2023-05-05.
[x] Unites States Geological Service, 2018, Drought and Groundwater Levels. https://www.usgs.gov/special-topics/water-science-school/science/drought-and-groundwater-levels. Accessed 2023-05-05.
[xi] International Water Management Institute, 2021, Utilizing Floodwaters for Recharging Depleted Aquifers and Sustaining Irrigation: lessons from multi-scale assessments in the Ganges River Basin, India. https://gripp.iwmi.org/wp-content/uploads/sites/2/2021/01/GRIPP-Case-Profile-Series-Issue-4.pdf. Accessed 2023-05-05.
[xii] California Department of Water Resources, 2018, Using Flood Water for Managed Aquifer Recharge to Support Sustainable Water Resources. https://water.ca.gov/-/media/DWR-Website/Web-Pages/Programs/Flood-Management/Flood-MAR/DWR_FloodMAR-White-Paper_a_y20.pdf. Accessed 2023-05-05.