Vernon's Flood Story

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Introduction

Flooding is a natural process that has always been an important part of the Okanagan's physical history. The area of the City of Vernon, located on the traditional Indigenous lands of the Sylix Okanagan and the Secwe̓pemc Peoples, is no exception. Our vibrant community was developed around BX Creek and Vernon Creek between the shores of Swan Lake to the north, Kalamalka Lake to the south, and Okanagan Lake to the southwest. The history of water through these systems is just as much a part of Vernon as the structures and roads that make up the city. 

Flooding provides many benefits, including the fertilization of agricultural land and replenishment of reservoirs used for recreation and vital water supply. That said, flooding is a powerful natural process that can present risk to people and infrastructure within flood-prone areas.

The City of Vernon has undertaken a detailed flood mapping study to better understand the potential impacts of flooding on our community.

The conclusions and recommendations of this study will guide the City of Vernon and its residents in the development and implementation of flood risk reduction strategies. 

Study Area

The flood mapping study examines flooding from BX Creek and Vernon Creek within the City of Vernon and the community of Priest's Valley 6.

Priest's Valley 6 is a Indigenous reserve of the Sylix Okanagan People, located on the shores of Okanagan Lake directly southwest of Vernon, along the downstream extent of Vernon Creek.

BX Creek drains from the BX Creek  watershed , which is situated northeast of Vernon. It has been examined in two parts: Upper BX Creek and Lower BX Creek. Upper BX Creek runs from the upper reaches of the watershed to the inlet of Swan Lake. Lower BX Creek drains from the outlet of Swan Lake to the  confluence  with Vernon Creek. The Province of BC manages lake levels in Swan Lake and flows into Lower BX Creek via a small damn at the outlet of Swan Lake.

Vernon Creek is fed from Kalamalka Lake to the south of Vernon and empties into Okanagan Lake southwest of Vernon. The Province of BC manages lake levels in Kalamalka Lake and flow into Vernon Creek with the Kalamalka Lake dam. Kalamalka Lake is connected at its southern extent to Wood Lake by a canal in Oyama. The two lakes are fed by  runoff  from the surrounding highlands. 

Study Area

Vernon's Flood History

Significant Events

Flooding has always been a part of Vernon’s history. This timeline outlines more recent records of key floods, sedimentation issues, and flood control projects affecting Vernon Creek, BX Creek, the surrounding lakes, and the city itself. 

Prior to 1892

Upper BX Creek was diverted to Swan Lake.

Prior to 1940

Flooding occurred near the 3200 block of Barnard Avenue (30th Avenue).

1959

Vernon Creek flooding in Polson Park (1959) while the Royal Family visits Vernon.

1976

The Okanagan Basin Implementation Agreement was executed between the Governments of Canada and British Columbia for the development and management of water resources in the Okanagan Basin.

1990

High water levels caused flooding along the shores of Kalamalka Lake and Okanagan Lake.

1996

The largest recorded flood on Upper BX Creek on May 31, 1996, resulting in high water levels on Swan Lake. The creek overtopped the Pleasant Valley Road culvert, the 48th Avenue culvert, and the 20th Street culvert north of 48th Avenue. This resulted in a washout of the 20th Street culvert south of 48th Avenue.

2012

The  Okanagan Lake Regulation System  was implemented to regulate water levels in the Okanagan Valley mainstem lakes (Kalamalka, Okanagan, Skaha and Vaseux) and flows through Vernon Creek and the Okanagan River. During freshet, high water levels on Swan Lake created flow over and around the Swan Lake Dam into Lower BX Creek.

2017

Flooding on BX Creek and extreme water levels on Kalamalka Lake and Okanagan Lake occurred due to heavy spring rainfall and snowmelt.

 

photos taken during the 2017 flooding event

2018

Flooding was comparable to the 2017 event. Emergency dredging was carried out downstream of the 48th Avenue crossing of Upper BX Creek.

2020

Heavy rainfall caused freshet flood conditions, including flows over and around Swan Lake Dam. Several areas in Vernon experienced significant flooding.

Causes of Flooding

Environmental Conditions

Freshet, Rain and Snow

Natural flooding in the Okanagan Region will most often correspond to the spring freshet. The spring freshet refers to the annual melting of the winter snowpack. During the most serious flooding, this snowmelt is enhanced by spring rainfall. Increased runoff leads to higher water levels in lakes, higher flows in creeks and rivers, and a greater amount of sediment and debris transported through creek systems.

Lake Water Levels

Lake water levels also play an important role in flooding. Swan Lake and Kalamalka Lake are dammed, and their outflows into Lower BX Creek and Upper Vernon Creek, respectively, are controlled by FLNRORD to manage a number of different factors, such as flooding, drought, water demand, recreation, and environmental concerns. In addition to human control, lake levels are influenced by runoff inputs from annual weather conditions, groundwater levels and water retention from previous years. Vernon Creek can also experience additional flooding at the downstream extent from  backwatering  if water levels are high in Okanagan Lake.

Sedimentation and Debris Obstructions

Sedimentation and debris obstructions also play a role in flooding, particularly on Upper BX Creek. Upper BX Creek is prone to transporting sediment and debris (such as downed trees, branches, and rocks) from the upper watershed during a flood, which can result in channel or crossing obstructions. Such obstructions have been known to lead to overland flooding and damage to crossing infrastructure. 

Impact of Climate Change on Flooding

It isn’t possible to know exactly how climate change will affect the magnitude or duration of future floods in Vernon. However, we can say that flooding will be less predictable in the future. Some factors, such as decreased snowpack accumulation in the winter and earlier melting in the spring, can be expected to contribute to lower freshet flows. On the other hand, rapid spring warming and increased spring precipitation could contribute to higher streamflow. Wildfires can lead to increased surface runoff, with the potential to lead to higher flood flows. Fires may also introduce excess sediment and could add to sedimentation and debris problems related to channel blockage. As such, for present-day resiliency planning, it is important to prepare for the possibility that future flood magnitudes, and resulting flood risk, may increase.

For more information about climate change around the City of Vernon, read the Pacific Climate Impacts Consortium  Climate Summary for Thompson/Okanagan Region .

Terminology

What are Flood Maps?

Flood maps display the inundation extents of potential flood events. The Vernon flood study area was analyzed through detailed  hydrologic  and  hydraulic  modeling to determine what those inundation extents would be. Two floods of different likelihoods were modeled:

•20-year flood: This is a flood that has an estimated probability of occurring on average once every 20 years (in other words a 5% chance of occurring every year).

•Design flood: Any planning, development, or construction within the floodplain should be intended to withstand the design flood. The recommended design flood is the 200-year flood (0.5% chance of occurring every year) on Vernon Creek, and the 1996 flood of record on BX Creek, which is of greater magnitude than the estimated 200-year flood on BX Creek.

Both flood models included an increase in flow to account for the potential future impacts of climate change.

The BC Local Government Act permits local governments to designate floodplains and set flood construction levels and setbacks to attempt to limit flood risks. Flood maps are a key factor in this decision-making process. Through detailed hydraulic modelling of the design flood event, two types of maps have been developed: floodplain maps and hazard maps.

Important Flood Mapping Terms

The primary flow path during a flood event. Typically, the floodway includes the stream channel and any floodplain areas that effectively convey flood flows.

: The flood affected area in the floodplain outside of the main floodway where water depth and velocity are low.

Refers to the elevation above which construction is recommended, after incorporating freeboard over the design flood water level. The purpose of an FCL is to protect property that would otherwise be susceptible to damage from floodwaters. 

Inundation extents: The extent of the entire area covered by any depth of water outside the stream channel during a flood.

Setback: Refers to the distance from the top of bank or natural boundary of a water body in which development should be prohibited or restricted to limit local flood risk.

Top of bank: means the same as Natural Boundary which is the visible annual high-water level reached during the mean flood event of any water course, typically determined onsite by a qualified professional.

Freeboard: A vertical offset from the design flood water surface to account for uncertainties and unpredictability regarding hydraulic, hydrologic, and geomorphologic properties. A freeboard of 0.6 m has been adopted for the City of Vernon Flood Mapping Project.

Flood construction level (FCL): Refers to the elevation above which construction is recommended, after incorporating freeboard over the design flood water level. The purpose of an FCL is to protect property that would otherwise be susceptible to damage from floodwaters. 

Flood Maps

Floodplain Map

The floodplain map shows the inundation extents from the detailed hydraulic modelling of the design flood, including 0.6 m of freeboard. Selecting a property on the map below will show whether the lot is included or excluded from the floodway and the flood fringe.

Flood Hazard Map

Hazard maps are used for flood mitigation planning, emergency response planning, and flood risk assessments. They show the flood depth and velocity from the detailed hydraulic modelling of the design flood. The hazard maps do not include freeboard. 

Taking Action

The following information is important for all Vernon residents, business owners, and visitors.

Stay Informed

It is important to be aware of potential flooding and how it may affect your home or business. Property owners are responsible for protecting their property from flooding and flood related risks.

During flood season (April to July), pay attention to weather conditions. A rapid increase in daily temperatures, significant rainfall, or a combination of both can potentially lead to flooding.

If your property is located adjacent a creek, be sure to monitor the creek regularly to ensure that you are aware of potential for flooding and flood-related risks. You may wish to engage a qualified professional to assist with this evaluation. 

Even if your home is not located right next to one of the creeks, it may still be subject to flood risk. While referring to the flood maps on this website may help you to identify whether you are in a potential inundation zone, the maps are not based on site specific studies. In addition, the flood maps are limited to the design flood event (estimated to have approximately a 0.5% chance of occurring in any given year); more extreme events, though unlikely, are possible and could have greater inundation extents than shown on the flood maps. If you wish to determine whether a specific site or lot is located in an area subject to flood risk, you should consult a qualified professional.

Keep in mind that flooding has the potential to impact all Vernon residents if it leads to infrastructure damage, loss of road use, disruption to services, etc. Be aware of flood conditions even if you don’t think your home is located in an at-risk zone. 

Stay in the Loop

The City of Vernon monitors flood indicators and takes steps to alert the public of potential or expected flood hazards when possible. You can check the  City of Vernon website  for updates. The River Forecast Centre also issues advisories and warnings about flood risks on their  Flood Warnings and Advisories  web page.

You can also sign up to receive emergency notifications and news updates through a City of Vernon  email subscription . You will be provided with alerts for flooding, as well as other types of emergencies such as severe weather or fires, so you will always be kept in the loop. Emergency information will also be made available through local media broadcasts and City social media pages.

Note that unexpected weather events and other hazards can cause flooding before public notification is possible. The City is committed to keeping the public as well informed as possible and provides updates to emergency information as it becomes available.

Getting Ready

If you think your home or business is in a flood hazard area, there are several things you can do ahead of time to reduce risk in the event of a flood.

If you are located adjacent to a creek or within/near the potential inundation zones indicated on the flood maps on this website, consider the following:

Research options for overland flooding insurance: the Province of BC advises that if a household could have reasonably and readily purchased overland flood insurance and did not, disaster financial assistance may not be available.

Protect your home and property through cost effective maintenance such as:

  • Clearing snow and pooling water away from foundations
  • Clearing debris from nearby storm drains
  • Storing important items in waterproof containers and/or on high shelves
  • Raising appliances
  • Install a non-return valve in sewage pipe to prevent sewage backflow

If you are able, consider home improvement projects for flood protection.

Resources for making your home more flood resilient:

Additional flood preparation resources:

What to do During a Flood

If flood risk warrants protective action to local properties, sand bagging materials may be available at the City of Vernon Operations building, located at 1900 48th Avenue. You should check in advance to determine the availability of the required materials and, if necessary, make arrangements with alternative providers. You can use sandbags to prevent or lessen flooding on your property. Check out this helpful video on how to build a sandbag dike:

How to Build a Sandbag Dike

If flooding is imminent or actively occurring:

  • Park vehicles away from streams and waterways
  • Never walk or drive through flood waters. Waters can be flowing more quickly or deeply than you expect and can be an extreme hazard
  • Avoid crossing bridges if the water is high and flowing quickly
  • Keep your radio on to stay informed about affected areas and what to do if an evacuation is ordered.

If you think you could be in an at-risk zone, prepare for a potential evacuation order by:

  • Collecting important documents
  • Assembling a 72-hour grab-and-go bag
  • Shutting off electricity to areas that are at risk of flooding (such as your basement or ground floor)
  • Moving electronics and important items to upper floors or to high shelves

For more guidance on what to do during a flood, refer to the  PreparedBC Guide for Staying Safe During a Flood  and the  Government of Canada Guide for During a Flood 

Evacuation Notices

In the case of an anticipated or imminent flooding emergency, the City of Vernon may issue an Evacuation Alert or an Evacuation Order. It is extremely important to heed these.

  • Evacuation Alert: Get prepared to evacuate the area under possible Evacuation Orders. Collect all important documents and prepare a 72-hour grab-and-go bag if you haven't already.
  • Evacuation Order: You are at risk and must evacuate the area promptly. An Emergency Reception Centre will be set up for evacuees if required.
  • Tactical Evacuation: Evacuate the area immediately. There is no time to make preparations as emergency conditions pose a threat to life and safety.
  • Evacuation Rescind: You may return home as immediate danger has passed, but stay alert in case the situation worsens again.

For more information on evacuation notices and what to do when an evacuation is in effect, visit the  www.vernon.ca/evacuationstages 

Additional Resources

City of Vernon Resources:

PreparedBC Resources:

Government of Canada Resources:

Vernon's Response

The City of Vernon has undertaken  mitigation  measures to reduce flood risk. These include:

  • Sediment Basins: Sediment basins for Upper BX Creek have been constructed downstream of Pleasant Valley Road and near 48th Ave at 20th Street. The development of a new sedimentation pond near the BX Creek Ranch Park is also planned for 2022.
  • Sandbagging: Sand and sandbags have been provided during flood events and have been used by residents as needed to protect their properties during flood season.
  • Flood Education: This flood story map was initiated as an educational tool to increase public awareness of flood risk and the associated risk reduction options.  The City of Vernon  website also contains many readily available information resources for flood risk education and emergency awareness.
  • Freshet Preparation: Freshet preparations include active monitoring of creek water levels, local snowpack reports, and weather and snowmelt conditions. Inspections and necessary maintenance are conducted for infrastructure such as roads, culverts, bridges, outfalls, and stormwater retention structures that could be impacted by increased water levels. Sediment is removed annually from the two existing Upper BX Creek sediment basins.
  • Emergency Management Program: This program is empowered to meet legislated responsibilities for directing and controlling local coordination of emergency response to, and recovery from, a major emergency or disaster. For more information on Vernon’s Emergency Management Program, visit:  https://www.vernon.ca/homes-building/fire-safety/emergency-management .
  • Streamside Maintenance Policy: This policy sets out the City of Vernon’s policy on streamside maintenance.
  • Flood Study: The City of Vernon has undertaken the Detailed Flood Mapping, Risk Analysis and Mitigation Study to increase understanding of local flood risk and inform future flood mitigation planning. 
  • Land Use Planning: The City of Vernon’s land use regulations and policies encourage for the maintenance, enhancement and restoration of natural assets that can provide ecological functions that mitigate the impacts of flood risks. As flood data and mapping information becomes available, the City would provide information to its development community. 

Mitigation

Future Plans

Flood risk mitigation can be achieved through a wide variety of actions and strategies. These include both structural/engineered actions (e.g., dikes and dams) and non-structural options (e.g., policies, programs, and initiatives). Based on the findings of this flood mapping study, the City of Vernon is exploring several new mitigation efforts that will make our community more resilient to future flooding.

01 / 08

1. Emergency Flood Response Plan

The City of Vernon is working on updating our Emergency Flood Response Plan to guide Vernon through the flood response process in the event of future floods. Pre-planning a response to potential flooding will ensure an efficient, safe, and effective response. The updated Emergency Flood Response Plan will include:

  •  Identifying key locations to monitor flows and water levels to trigger emergency plan actions;
  • Pre-planning locations for temporary community flood barriers and culvert blockage clearing during high-water events;
  • Refining evacuation routes based on the updated flood hazard mapping; and
  • Recovery planning for after flood events.

2. OCP and Zoning Bylaw Updates

The City of Vernon will use the flood maps from this study to establish flood bylaws that will provide guidance for development within the floodplain, or will update the existing OCP and Zoning bylaws with restrictions to development within the floodplain.

3. Sediment and Debris Management Plan (Upper BX Creek)

There is a well-documented history of sediment transport and the associated flood risk on Upper BX Creek. The existing sediment and debris management plan will be updated to consider sediment loading on Upper BX Creek. Two sediment basins are already established downstream of Pleasant Valley Road and between 48 th  Avenue and 20 th  Street. A third sedimentation pond is to be constructed in 2022 in the BX Ranch Dog Park, which will provide the City with increased protection from sediment and debris. 

4. Diking between 20th St. & Deleenheer Road (Upper BX Creek)

The residential area between 20 th  Street and Deleenheer Road is susceptible to flooding from Upper BX Creek. The west bank of the creek has several low points through this section, and during high flow events, water can leave the channel and flood the residential area. Diking along this section of the creek is expected to provide effective flood mitigation: this is demonstrated by the slider map, which compares the design flood extents under existing conditions to the extents with a new riverside dike in place. The City is considering a diking upgrade in combination with crossing upgrades at 20 th  Street and 48 th  Avenue (see Mitigation item 6, below).    

5. Crossing Upgrades

43rd Street, Okanagan Landing Road and Lakeshore Road (Lower Vernon Creek)

Three undersized culvert crossings have been identified on Lower Vernon Creek. These crossings have limited capacity and cause backwatering and overbank flooding under high flows. Upgrading the crossings to clear-span bridges with adequate capacity reduces flood risk in these neighborhoods.

43rd Street

Overbank flooding caused by backwatering at the 43 rd  Street crossing impacts six residential roads and approximately 50 properties under design flood conditions. Upgrading the crossing is expected to greatly reduce these impacts, as shown in the slider map.

Okanagan Landing Road

Overbank flooding at the Okanagan Landing Road crossing could impact approximately 80 properties, five residential roads, and Okanagan Lake Road itself under design flood conditions. Upgrading the crossing will mitigate flooding on the roads and is expected to limit the number of impacted properties to approximately ten.

Lakeshore Road Crossing

The extent of overbank flooding around the Lakeshore Road crossing is very dependent on water levels in Okanagan Lake, which backwaters Lower Vernon Creek. As such, the design flood was modeled under four different crossing / lake level scenarios to assess the benefits of upgrading this crossing.

modelled the existing culvert crossing with the design water surface elevation on Okanagan Lake (343.9 m). Approximately 140 homes are flooded under this scenario.

modelled the upgraded crossing with the design water surface elevation on Okanagan Lake (343.9 m). With the improved crossing, approximately 50 fewer homes are flooded compared to Scenario 1.

modelled the flood event in Vernon Creek + 341.9m Okanagan Lake pool elevation (this elevation is comparable to the lowest lake level likely to occur during the freshet period) on the existing crossing at Lakeshore Road and found 105 homes would be flooded.

modelled the upgraded crossing with the lowered Okanagan Lake water level of 341.9 m. With the improved crossing, approximately 95 fewer homes are flooded compared to Scenario 3. 

6. 20th Street and 48th Avenue crossings

Three additional undersized culvert crossings were identified on Upper BX Creek, which cause backwatering and significant overbank flooding under high flows. These are located at 20 th  Street south of 48 th  Avenue, 48 th  Avenue and 20 th  Street, and 20 th  Street north of 48 th  Avenue. Upgrading these crossings to clear-span bridges with adequate capacity reduces the flood risk in these neighborhoods.

shows the design flood extents with the existing crossings.

shows the approximate design flood extents if all three crossings were to be upgraded to clear-span bridges.

shows the approximate design flood extents if all three crossings were to be upgraded to clear-span bridges and the diking between 20 th  Street and Deleenheer Road were completed (see Mitigation item 4, above).

 

More Information

This flood story has been developed as part of the greater City of Vernon: Detailed Flood Mapping, Risk Analysis and Mitigation study, completed by Northwest Hydraulic Consultants Ltd. The project reports are available here:  www.vernon.ca/floodstory 

Use and Limitations

The content presented in this website are subject to the terms and conditions as detailed below.

The information provided on this Vernon Flood Story Map is for general information purposes only. The City of Vernon and Northwest Hydraulic Consultants Ltd. make no representations and warranties of any kind, express or implied, regarding the accuracy, adequacy, validity, reliability, availability, or completeness of any information in the Flood Story Map or referenced on this site. 

Information on this site:

  • is general information provided to improve understanding of local flood hazards;
  • is not a substitute for independent professional advice;
  • is subject to the uncertainties of scientific and technical research including study limitations, assumptions, and caveats;
  • may not be accurate, current or complete;
  • is subject to change without notice; and,
  • may include views or recommendations which do not necessarily reflect the views of the City of Vernon or NHC or indicate a commitment to a particular course of action.

Refer to the project reports for full limitations of the information presented.

The City of Vernon and Northwest Hydraulic Consultants Ltd. (NHC) are not liable to any person for any damages, injury, loss, or death arising directly or indirectly from using this site or any information or material on this site, or from any action or decision taken as a result of using the site.

The information and materials on this site or referenced by this site do not constitute professional advice, you should consult your qualified professional for specific advice relevant to your circumstances.

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