Preparing for the future using hydrodynamic modeling.

An Interview with:

Daniel Chadwick, P.Eng. and Ann-Marie Giesbrecht, P.Eng.

Ann-Marie Giesbrecht is a structural engineer working out of CWA’s Vancouver office who has acted as the Project Manager for the Indigenous Services Canada & Skidegate First Nations Coastal Vulnerability Studies since 2017. The studies, which are now entering into their fifth and penultimate phase, are assessing the vulnerability of key infrastructure within First Nations’ coastal communities to the effects of climate change (sea level rise), storm surge, and earthquake-induced tsunamis.

Daniel Chadwick, also working out of CWA’s Vancouver office, is a structural engineer  specialized in structural design in marine environments. He has been involved with the studies since 2017. Thus far, Daniel has visited sixteen of the sixty First Nations communities involved in these studies along the northern and central coasts of British Columbia, performing site visitations and data collection. During his visits, Daniel has also gathered information on traditional First Nations oral histories, as well as photographic documentation of existing infrastructure that is of cultural and/or economic importance to the communities involved in the studies.

Who is involved in the Coastal Vulnerability Studies and what is the goal of these studies?

Ann-Marie: In order to help coastal First Nations communities in British Columbia prepare for flooding caused by climate change and natural disasters, CWA Engineers, CMO Consultants, and Robin Fenn Consulting are completing vulnerability studies with funding from Indigenous Services Canada.

The studies aim to evaluate the vulnerability of critical infrastructure in coastal communities to inundation and flooding caused by sea level rise, extreme storms, and tsunamis. Flood levels are determined by setting up models and running simulations for various storm and tsunami events. From these models, the maximum water levels are plotted onto georeferenced aerial photographs of each community to identify which infrastructure is at risk of flooding.

Can you describe the type of modeling you are doing?

Daniel: We use a software called MIKE21, which is a hydrodynamic computer modeling software. There is a vast amount of information that we input into the model which is used to run simulations that can take days or even weeks to produce results.

We generally have a standard process that we follow, where we first go out and obtain high resolution aerial photos of each community, and then, as Ann-Marie mentioned, these are georeferenced by attaching survey data. We also collect imagery data of the bathymetry (under water topography) adjacent to the communities, which is basically a 3D underwater map of the ocean floor.

This information is then, essentially, stitched together with the aerial survey to create a model of the community. We also input information obtained from the weather stations near the communities, including wind data, river flows, and tides, which we input as boundary conditions into the model.

Another important input is sea level rise. We obtain this information from a series of reports that have been produced by the Department of National Resources Canada, projecting sea level rise to the year 2100. We take those sea level rise values and add them to the tides/water levels during the modeling.

Once all those pieces are combined into the model, we add in forcings such as earthquakes and wind, and then run simulations to see what the effects are going to be like on the community. When we have finished running  these simulations, we then take the flooding results and overlay them onto the aerial photographs to identify the individual pieces of infrastructure that are being impacted.

There is an enormous amount of data being inputted into the model, and it takes the better part of six to seven months for the team to complete this work for each phase. The phases include up to six neighbouring communities that we create a single model for, allowing us to then look at the region as a whole. Each phase builds on the model from the previous phase, so each year we are adding more and more data into this very large model.

CWA is performing half of the modeling, covering everything on the north coast of BC down to the Lower Mainland, as well as the east coast of Vancouver Island. The other half is being performed by another consultant, Parsons, who is covering the communities on the west coast of Vancouver Island. So far, CWA has completed modeling for twenty-five communities. We typically run modeling for five to six communities a year, and we estimate that all studies will be complete in one to two years.

Once the studies have been completed, how many communities will you have modelled?

Ann-Marie: We are currently wrapping up Phase Four. Each phase takes approximately a year to complete. In total, the whole project will involve sixty communities, and as Daniel mentioned, CWA is modeling about half of them. We are looking forward to starting work for the final phase next year.

What are some of the greatest threats to BC’s coastal communities in terms of climate change?

Daniel: As far as climate change is concerned, sea level rise is the number one threat. These coastal communities have dealt with storms and tsunamis for centuries. However, with sea level rise now in the equation, the effects of storms and tsunamis are going to be even worse due to the increasing water level.

It is challenging to predict exactly what the sea level rise will be in the future because many of the factors contributing to sea level rise are related to human activity. We are not able to say with any certainty whether human habits are going to change significantly by the year 2100, and whether it will be too late at that point to stop the rapid increase in sea level rise. The sea level rise graph increases exponentially, and so at some point I think we are going to kind of go off of an edge, after which it’s likely that even any significant changes we make to our habits probably won’t have much impact.

Have the communities that you are studying already begun to feel the effects of climate change?

Ann-Marie:  Yes, I think so. There is nothing very quantitative yet, so to speak, but we have definitely seen qualitative evidence in speaking with the community members. They have said that storm events seem to be getting more significant and that flooding has become more of an issue for them in recent years. It most likely has to do with sea level rise and the effects of climate change.

One of the ideas that commonly gets raised during community discussions is to establish monitoring programs adjacent to the communities in order to measure tides, winds, etc. in future years. The modeling can then be refined to better predict flooding in the community and quantify the effects of climate change as it’s happening.

Daniel, you have visited these communities and spoken to the people living there — what have they said about what is happening in their communities in relation to climate change? 

Daniel:  In some communities, different species of fish have started to appear or disappear from their waters. Certain species of fish that have been around for as long as people can remember seem to be disappearing, while fish that are associated with tropical waters are starting to appear. And as Ann-Marie said, we have heard anecdotal evidence that storms seem to be much worse than they used to be and that the waves seem to be bigger.

Most community members spend their entire lives on the ocean. Fishing and spending time out on the water is a very important part of their culture, and so they are very attuned to how large the waves get. These days they are starting to see waves that are several feet higher than they can remember having seen as children, and they have observed that, overall, the effects of water are more severe than they used to be.

CWA attends a workshop every year with the First Nations involved with the studies. We come together to discuss adapting to climate change. All the communities tend to be very receptive to it because they can see the effects already —  they see what is happening around them. They want to stop talking about whether climate change is actually happening and start talking about what they can do about it.

Ann-Marie, can you tell us a little more about what takes place at these workshops each year?

Ann-Marie:  Yes, the annual workshop is a meeting held with all the communities involved in each phase of the studies. We invite community members to the Lower Mainland at the end of the phase to participate in workshop activities and discuss how to use the reports. The reports that we create are based on our model findings, which are highly technical in nature. The workshops provide an opportunity for us to present the findings to the community members and show them how the information can be interpreted.

We walk the participants through various activities, showing them how to use the flood maps and where to go in the reports to find certain information. We identify what areas are prone to flooding and what hazards are present, such as whether the community is susceptible to multiple waves or perhaps just water inundation. The intent of the workshop is to enable the communities to use the information contained in the report to make emergency response plans and community plans that will facilitate adaptation to the changes taking place within their local environment.

Daniel, what issues will these communities likely face in the future, and when can they expect to see greater effects in their environments due to climate change? 

Daniel:  I would say that, other than the increase in the number and severity of storms and tsunamis due to the higher water levels, another issue is the amount of land that is available on the First Nations reserves. They have a fixed amount of land that they can work within, and now that land is shrinking due to the rising water level.

Their homes are being encroached upon and they are having to contend with the likelihood of having to move these homes. But in some cases, they don’t even have the room to move them back because they have this very defined parcel of land. This issue touches upon the highly political issue of land title, where First Nations are having to renegotiate whether they can expand these parcels of land, whether they can trade it for another spot, etc.

Another sensitive issue is that, with the land receding or the water encroaching, a lot of cemeteries in these communities are now located close to the shoreline. When these burial sites were originally created, they were set a good distance back from the shoreline, but with the shoreline receding significantly over the past several decades, some of these burial sites are being uncovered. So, these communities are facing the dilemma of whether to keep the burial sites where they are or to whether to disrupt them in order to preserve their ancestors’ remains. Unfortunately, it is really a losing battle either way.

Ann-Marie, you have seen the evolution of the models over several years now — what are the models telling us?

Ann-Marie:  The risk of flooding varies drastically for each community. Some communities are more susceptible to flooding caused by storm events, while others will see increased inundation from tsunamis. The probability and extent of flooding is heavily dependent on a variety of factors related to each community’s location, including the local bathymetry and topography, the proximity of their community to the ocean and tectonic fault lines, and whether the community is exposed or sheltered from wind events, to name a few.

The magnitude, quantity, and timing of tsunami waves resulting from earthquake events also varies for each event and at each community. Some communities may see a massive single tsunami wave, while others will see multiple smaller waves extended over a period of time.

Daniel, what types of infrastructure do you assess when you visit the coastal communities involved in these studies?

Daniel:  Certain types of infrastructure are generally common to all communities. There is usually an administration office in each First Nations community, and there might also be a museum, and a community hall or a Big House, which serves as the traditional gathering centre.

Most will have lift stations for the pumping of wastewater throughout the community, which is something we are always sure to assess. These lift stations are typically at a very low point because they are designed for the wastewater to drain to that low point and then pump upwards. Due to this, in practically all communities the lift station is something that will potentially be impacted, so we always look for those.

There are also some other interesting and unique assets that we look at such as carving sheds and also fish plants for the commercial processing of catch.

We generally try to identify and assess any infrastructure that is either culturally or economically important to a particular community. We tend to steer clear of houses, as this is generally not part of the studies’ scope. However, sometimes we will identify a general store,  or something of that nature, if it is considered vital to the daily lives of people in the community.

Part of the project’s mandate is to gather historical and traditional knowledge from the local community members. What have you learned about their communities?  

Daniel:  In every community that we visit we always like to ask, one, if there are any elders that we can talk to who were around in 1964, and two, whether they were old enough to remember what happened back then.

1964 was the year of the last big earthquake event in living memory, known as the Great Alaska Earthquake. It was a 9.2 magnitude megathrust earthquake that occurred in south-central Alaska, near the town of Anchorage. It is the most powerful earthquake that has ever been recorded in North America’s history and the second most powerful earthquake in recorded world history.

The earthquake caused devastating tsunami waves that came down into BC. The town of Port Alberni, which is located at the end of a narrow 40-kilometer inlet, suffered the most damage and was almost completely wiped out by two powerful waves. At around midnight the tsunami wave generated by the Alaska earthquake travelled up the inlet and, in the process, became amplified in strength and intensity through a sort of funnel effect. The initial wave had a height of almost 2 meters and the second wave that hit an hour or so later was just over 3 meters.

So, when we go on site visits, we ask if anyone in the community was around during the time of the 1964 earthquake and what they remember about this event. We have asked about this in several communities.

Most of the elders were kids when it happened. People in some of the communities were warned of the tsunami over their ham radios, which were quite popular at the time. People in Alaska used their ham radios to warn people that there was a tsunami coming. We have heard very consistently from the locals who remember the ocean receding very rapidly, and then coming back in very rapidly at a much higher level. It was not this Hollywood style crashing wave that you might expect to see in the movies.

Several locals recounted that the water went out so far and so quickly that dozens of fish were left floundering about on the exposed seabed. Some locals remember running out and trying to grab the fish, but of course this was a very dangerous way to fish! This is, in fact, a typical characteristic of tsunamis — they create a vacuum effect as they rapidly approach the coastline, sucking all the water back towards the sea, and leaving the seafloor exposed prior to the wave hitting.

In our computer model simulations, the height of the wave varies in each community. One of the simulations that we run is the 1964 Alaska earthquake, but we also run simulations at the year 2100, because of the likelihood that this type of earthquake will happen again in the future.

In the 2100 simulation we find in some communities that the waves range from approximately one to two meters above sea level. However, it is often not just the governing event that will affect the size of the wave, but other factors as well, such as the local topography and bathymetry, as was the case in Port Alberni. As Ann-Marie mentioned, it really is unique for each community, and the height of the wave can vary dramatically. There is an infinite number of earthquakes that might occur around BC and each one could produce a different tsunami, so we have taken the likely worst-case scenarios and have modelled those.

We hear everyone talking about the “Big One” in the news these days. Scientists predict it will happen sometime over the next two-hundred years, emanating from the Cascadia Subduction Zone, which tends to be the governing event. We are using the 9.2 magnitude 1964 Alaska Earthquake for the purposes of our modeling, because earthquakes have different statistical return periods. The magnitude of the one that actually does hit could vary quite a bit. It could be an 8.8 or it could be a 9.2 magnitude earthquake. You just cannot be certain which one you are going to get.

The earthquake event that occurred on the Cascadia Subduction Zone is an event that occurs roughly every five-hundred years and the last time that it happened was in the year 1700. Of course, there are no written records from these local regions of BC from that time (although some written accounts, which are connected to this same event, do exist in Japan). During the course of these studies, we were hoping to come across some First Nations’ oral histories related to that event, possibly even tying the earthquake in 1700 to a local historical landmark. Unfortunately, thus far, we have not been able to uncover that level of detail, but we still have many more communities to visit…

While we  ourselves haven’t yet come across this anecdotal evidence, Ethnographic researchers conducting studies in the 1990’s and early 2000’s showed that the oral histories of the First Nations people that have lived along BC’s coast for centuries share strikingly similar accounts of a catastrophic earthquake and tsunami event that took place many generations ago. The combination of this archeological evidence, combined with other geological evidence, has led researchers to determine that 1700 is the year in which this catastrophic earthquake event occurred.

How will First Nations communities use the modeling results to make their communities safer and to mitigate the risks they are facing due to climate change?

Ann-Marie: Awareness is the first step when you are trying to mitigate risk. With these studies, we aim to identify the specific flood related risks that each community faces by determining the extent of expected flooding through our models, and to identify which critical infrastructure will be impacted on our flood maps.

For the at-risk infrastructure identified on the flood maps, communities must decide which approach they wish to use to mitigate the risk – protection or relocation – and incorporate this into their future community planning, for example, by setting aside funds for future projects. Many factors will need to be considered, including the extent of flooding expected, the age of the infrastructure, whether it requires refurbishment, upgrades, or replacement, the costs of each option, and community preferences to name a few. The flood maps are one of many tools that can be used for future community planning.

As part of these studies we looked at the timeline for tsunami waves to reach each community. The magnitude, frequency, and timing of waves resulting from earthquakes varies for each community. Some communities will have more time before the initial wave reaches them, while others may be hit by multiple waves. Communities can consider the results of their study when developing or updating their emergency response plans, including the timing and duration of evacuations.

We recognize that the scope and focus of these studies is somewhat narrow, in that it is limited to flooding caused by climate change, storm events, and tsunamis. In fact, flooding can be caused by a variety of other factors, including landslides, glacial melts, and deforestation to name a few. Our results show just some of the potential vulnerabilities for these communities. As such, we recommend that further studies be completed to identify the broader spectrum of hazards that have the potential to cause flooding for each community.

The information gained from the Coastal Vulnerability Studies is really the initial step in the process of planning for future projects within the community. By first identifying the current condition and potential risks to the community’s assets, they can then begin to plan, prioritize, and budget for future projects and developments that will enable them to protect their communities’ economic and cultural assets.

 

View further details on the Coastal Vulnerability Studies HERE