Courtenay River Municipal Natural Assets Initiative

The City of Courtenay applied to undertake this project with the Municipal Natural Assets Initiative (MNAI) in order to understand how natural assets in the Courtenay River corridor could help mitigate flood risks, especially in the downtown core, and to see how they compare to engineered alternatives in terms of costs and benefits.

The City of Courtenay lies on the east coast of Vancouver Island in British Columbia within the traditional lands of the K’ómoks First Nation. The Tsolum and Puntledge Rivers converge into the Courtenay River, which flows into an estuary where the City is located. The low-lying areas near the rivers and estuary comprise the flood plain, which is subject to flooding. Historically, much of the City’s development occurred in the flood plain and the City has been experiencing increasingly frequent and intense flooding that impacts transportation corridors, businesses, and public and private properties.

The project developed four scenarios to determine how natural assets could mitigate flooding: widening the Courtenay river, naturalizing a former sawmill site, reinstating natural flow paths in the Courtenay river, and removing at-risk buildings from the flood plain. The project modelled these options individually and in combination.

The City of Courtenay has been building a strong asset management program for several years already. In 2013, it assessed how three engineered infrastructure options (dikes) could protect the Ryan Road commercial area from flooding. Building on that study, the City then wanted to explore how natural assets could protect their downtown core and minimize damages and losses.

Understanding and Assessing Impacts

Climate change is expected to increase the frequency and magnitude of flooding, as precipitation patterns change and sea levels rise. Throughout the last 10 years, increased flooding in the Courtenay River system has demonstrated local vulnerabilities, and the need to assess and improve existing levels of flood protection. Flood events in 2009, 2010 and 2014 affected key transportation corridors, Lewis Park, the Ryan Road commercial area, and other private and public properties.

In response to the flood events in 2009 and 2010, the City conducted a Flood Management Study in 2012/2013, funded by a grant from Emergency Management BC. This study included an analysis of flood flows and tide levels at various flood return-periods concluding that peak flood levels could increase by 1.1m and 2.4 m by 2100 and 2200 respectively, and that storm surge peaks could increase by 15% by 2100 and an additional 15% by 2200. Flooding tends to occur in the downtown core with flood events greater than 1:20 years. Preventing damages from present-day and far greater 1:200 year flooding events will take a concerted large-scale, community-wide effort. The figure below depicts 2014 flooding in the downtown area.

The City experiences multiple flooding scenarios including those resulting from:

  • High tides / storm surges coming inland,
  • High water flows coming downstream as a result of precipitation, and
  • River flows influenced by BC Hydro dams

These events can happen simultaneously during winter months or individually. Practically, this means that flooding can come from upstream or downstream of the business district. Orthographic information suggests that the flow of the river has been constrained and diverted from its historical trajectory. This may contribute to the scale and nature of the flooding and also present options for its relief.

Identifying Actions

MNAI’s natural asset methodology follows the standard asset management process of assess, plan, and implement steps, highlighting novel considerations required for local natural assets and associated services. MNAI’s process begins with an initial engagement session with local government representatives including Parks, Public Works, Geographic Information Systems, Engineering, Planning, Water and Wastewater, and Finance. During the initial engagement session, plans and priorities of the community are discussed, key natural assets within the jurisdictional boundaries of the community are identified along with the important services those assets provide. The objectives of this initial engagement session are to identify:

  • Natural asset(s) that will be the focus of the natural asset assessment
  • Geographic boundary/ies of the focus assets
  • Skillsets and expertise of relevance to the natural asset assessment
  • Local government personnel that will engage in the assessment process
  • Data needs of the assessment and the sources for the relevant data

Following the initial community engagement session, the MNAI team works with local government partners to complete a natural asset assessment. This involves:

  1. Defining the scope of natural assets to be considered
  2. Inventorying and conducting a condition assessment of the assets
  3. Quantifying existing service levels from the assets, as well as co-benefits
  4. Quantifying the financial value of the natural assets if the services they provide had to be delivered by an engineered alternative
  5. Developing scenarios to explore alternative management plans and future implications for existing service levels
  6. Quantifying services levels under alternative scenarios
  7. Developing operation and management (O&M) plans based on existing conditions, risks, and desired service level trajectories

The 2013 Flood Management Study assessed three engineered infrastructure options (dikes) to mitigate flood impacts. The options focused on providing flood protection for the Ryan Road commercial area. They are: 1. Tsolum River flood wall: a constructed floodwall to provide protection for smaller and more frequent events (1:20 to 1:50 year events) but not protection for the larger 1:200 year event. 2. Ring dike: raising old island highway and Highway 19A to provide improved flood protection for extreme events (1:200 year event). Properties outside the dikes would require managed retreat, and the dikes may create increased flood depths upstream. 3. Partial ring dike option: similar to the ring dike (option 2 above), with the addition of a floodway over Comox Road. The floodway would allow overland flooding to neighbouring agricultural lands. The Study did not model the impacts of natural solutions for flood mitigation, such as providing alternate river flow paths or channel widening. Stakeholder consultation conducted during the study demonstrated strong interest in natural flood management solutions.



Four options for flood mitigation from natural assets were identified for assessment:

  1. Courtenay River widening: This option requires the removal of existing sheet pile dikes and sloping the banks of the Courtenay River to widen and naturalize the full length of the river channel. This option would potentially allow for additional water storage and conveyance capacity to the estuary, while also reducing some of the City’s responsibilities for maintaining the existing dikes.
  2. Kus Kus Sum: This option involves the naturalization of a former 3.36 hectare sawmill site to reinstate the natural foreshore and water flow paths (a project known as Kus Kus Sum). This project is currently being led by the K’ómoks First Nation, the City of Courtenay and Comox Valley Project Watershed Society together with Interfor Corporation (who currently owns the property). There are many environmental and social benefits related to this project, but specific benefits to flood mitigation have not been modelled. Kus Kus Sum could potentially allow for additional water storage and conveyance capacity to the estuary.
  3. Reinstate natural flow paths: As identified previously, much of the historic development in the City occurred in the floodplain, leading to channelization and in-fill of the Courtenay River. This option involves opportunities for reinstating natural flow paths or connecting new flow paths. This option could potentially allow for additional conveyance capacity to the estuary.
  4. Managed retreat: This option involves a gradual managed retreat of the full impacted floodplain over time, and allowing only land uses compatible with flooding in the floodplain. It would require extensive land acquisition and remediation but would mitigate undesirable impacts of flooding.

The flood modelling conducted by MNAI produced flood depth surface outputs for a series of flooding scenarios. For the scenario analysis, the following two flood events were defined:

  1. Flood Event A – based on the 2009 flood conditions.
  2. Flood Event B – based on the following assumptions:
    1. 1:200 year flood conditions in Tsolum and Browns Rivers
    2. Puntledge river under maximum release rates
    3. Tide of Medium Water Large Tide (MWLT)
    4. No storm surge and no climate change

The analysis for these two events also considered varying flood depth surfaces to understand a host of flood scenarios. A fifth scenario was also defined assuming retreat and relocation of properties impacted by the 2009 flood event. In this scenario, no additional flood depth surfaces were required. However, this scenario would significantly mitigate flood risk, while providing an opportunity to improve the natural assets within the City of Courtenay.

Outcomes and Monitoring Progress

Given the significant flood risk exposure to built assets within the City of Courtenay, a managed retreat and relocation of the built environment would dramatically reduce flood risks. This was the focus of the 5th scenario. In this scenario, it was assumed that any building impacted by the Flood Event A (the extent and depth of the 2009 flood) would be relocated. The total assessed value of impacted properties is approximately $6.8 million dollars. This is a rough indication of the cost to purchase these properties. These properties represent a total of 8.4 ha of land that could be naturalized under the retreat scenario. Additional costs associated with this scenario include:

  • Demolition costs
  • Costs of reconstruction outside of flood risk zones (however, the purchase of the existing properties should provide significant capital to property owners to offset some of the reconstruction costs)
  • Naturalization costs

The flood modelling conducted by MNAI produced flood depth surfaces for a series of flooding scenarios. From these scenarios, four flood depth surfaces were developed. The modelling results of the flood damage assessment revealed that under the 2009 flood conditions, natural asset improvements would reduce flood damages by $723,000. Considering a larger, more extensive flood event, natural asset improvements would reduce flood damages by $2.4 million dollars. The values presented above exclude a range of important co-benefits. The values alone also do not speak to the ongoing monitoring, operating and maintenance costs associated with each scenario modelled.

It is important to consider co-benefits when incorporating assets into an asset management plan. Economic and policy decisions that focus narrowly on the economic trade-offs between conventional infrastructure and natural assets may overlook a number of benefits associated with natural assets. While time and capacity restrictions did not allow the City to identify relevant co-benefits for the natural assets under consideration, such co-benefits likely include access to green and recreational space for residents, hydraulic detention, and water quality functions.

Next Steps

The City of Courtenay’s flood management and mitigation study and integrated rainwater management plan are in development. As such, the City is still exploring a range of options for the best approach to mitigate flooding in the project area. This analysis demonstrates that natural asset improvements alone are not sufficient to significantly reduce flood risks for the City. Engineered and natural asset management strategies are required, with three options being possible:

  1. Option A: Fully engineered – Ignore natural assets, and focus solely on major engineered flood protection infrastructure. 2.
  2. Option B: Engineered and Natural approach – Leverage natural assets to the extent possible to minimize the level of engineered flood protection required.
  3. Option C: Full Natural approach (i.e. retreat/relocation) – Invest significantly in restoring the natural floodplain by retreating/relocating in the areas of the City that are at the greatest risk.