This edition is devoted to the recently released major review of the flood events that occurred in the Spring of 2019. Flooding in our Township can have a major impact on our local economy and to the value of our real estate. This Snapshot is much longer than our usual reports, but we felt it was important to bring this pertinent information to the attention of those of our members who have a direct interest in or who have been impacted by the flooding.
Following the flood events, the Government of Ontario ordered a thorough review to determine the root causes and to seek recommendations on flood mitigation and land use policies. The review entitled An Independent Review of the 2019 Flood Events in Ontario, has now been published. The full 157-page study covers all of Ontario and can be viewed online using this link: https://www.ontario.ca/page/independent-review-2019-flood-events-ontario
The report makes 66 recommendations which can be found by using the link above. Of note, there are no recommendations regarding specific infrastructure changes (dams, reservoirs, channels, bridges, etc.). Recommendations that we feel are the most immediately pertinent for our members are: 29, 35, 37, 56, and 57. Below we have reprinted in italics the highlights of the report that pertain to our geographic area:
Ontario has a long history of taking actions to keep people and property safe from the impacts of flooding through land use planning policies and mitigative activities…However, during the spring of 2019, heavy rains paired with melting snow and a sudden temperature increase led to devastating flooding across many areas throughout northern and southern Ontario. Emergency declarations were made by 23 municipalities and one First Nation, with significant flooding impacting households, commercial properties, roads and other key infrastructure, such as bridges. Emergencies were first declared starting in early April and lasted through July in many cases. Even through the fall and heading into winter, the Great Lakes continue to experience high-water levels that have been underway since early 2017, and many people and properties continue to be at risk.
Contrary to what was quoted in local media at the time, the report goes on to say:
Based on an analysis of the information available for all of the systems that experienced flooding in 2019, nothing points to human error or the negligent operation of water control structures as the cause of the flooding. The sheer amount of water (snow and rainfall) on the landscape directly contributed to the flooding. Measures taken by water managers everywhere were effective in reducing the magnitude of flooding and associated damages throughout the drainage basins.
Section 4.3 of the report discusses the Muskoka River Watershed in particular. Here is some of what it has to say:
The drainage basin encompasses an area of approximately 5,100 square kilometres and extends in a southwesterly orientation for a distance of approximately 210 kilometres, descending 345 metres in elevation from the western slopes of Algonquin Provincial Park, to its mouth at Georgian Bay of Lake Huron. The watershed originates along the height of land known as the Algonquin Dome and is comprised of three drainage systems, including the North and South Branches of the Muskoka River and the Lower Muskoka subwatershed, and includes 200 lakes covering an area of approximately 78,000 hectares. The Muskoka River is comprised of 19 quaternary basins that form its subwatersheds. The three largest lakes in the watershed include Lake Rosseau, Lake Muskoka and Lake Joseph. The Muskoka River watershed is a complex, cascading system. There are a series of notable constrictions or pinch points that impede the flow of water and cause water to back up, creating what is referred to as a backwater effect, as affected by the hydraulic conditions. Think of it like a funnel, where discharging a large volume of water is limited by the narrowest and/or shallowest point in the river. Putting water into the funnel at a larger volume than can pass through the tip of the funnel causes it to rise up the funnel and overflow. Lake Muskoka is the last major lake in the system before water enters the Moon and Musquash rivers that flow into Georgian Bay, which represents the outlet of the funnel. All water from both branches of the Muskoka River and Lakes Rosseau and Joseph flow into Lake Muskoka, and the only outflow for Lake Muskoka is through the two dams at Bala. The MNRF Bala dams control the water levels on Lake Muskoka; however, during periods of high flows and levels, a difference in water levels develops between Lake Muskoka and what is known locally as Bala Bay. This is caused by three constrictions at Bala Park Island and Wanilah Island that restrict flow into Bala Bay, affecting how much water can be discharged from the Bala dams. During periods of flooding, a significant difference in water surface elevation (≥ 1 meter) is observed between Bala Bay and Lake Muskoka, which further exacerbates efforts to move water through the dams at Bala.
Muskoka is governed by a two-tier municipal system with the District Municipality of Muskoka as the regional municipality forming the upper-tier, working with the six area municipalities including the Towns of Bracebridge, Huntsville and Gravenhurst, and the Townships of Lake of Bays, Georgian Bay and Muskoka Lakes making up the lower tier. Of the approximate 150,000 people populating the watershed, approximately 58% are seasonal residents according to the 2011 Canadian census. The majority of the big three lakes—Muskoka, Joseph and Rosseau—are located within the Township of Muskoka Lakes. The Wahta Mohawk and Moose Deer Point First Nations are also located within Muskoka’s boundaries. There is extensive development with high value infrastructure within the main Muskoka Lakes (Lake Muskoka, Lake Rosseau, Lake Joseph, etc.) spread over approximately 14,000 lake lots, including 5,300-5,500 boathouses, greater than 6,500 docks, and approximately 41 marinas and 131 resorts.
There are 42 water management structures within the Muskoka River drainage basin, including dams and/or dam-powerhouse combinations in addition to three navigation locks. The MNRF operates 29 of these structures, all of which are manually operated using stop logs or valves. Most MNRF dams were originally constructed to facilitate the transport of logs to sawmills, divert water to power the mills, and aid in commercial navigation. Over the intervening years, the operations emphasis of the dams has transitioned from commerce and transportation to the provision of a balance of social/recreational, environmental and economic interests. It must be emphasised that dams in central Ontario, including those in the Muskoka River watershed, are not flood control structures. Flood control structures require a large lake or reservoir and associated drawdown capacity to store or hold back flood waters. Analyses have confirmed that lakes in the Muskoka River watershed that are regulated by dams have a limited capacity to drawdown water to affect flooding, and during periods of large volume rapid runoff, the available drawdown capacity is insufficient to reduce peak flood water levels. In this sense, the greater the magnitude of the flood event, the less ability the MNRF has on affecting or mitigating flooding through operation of its dams. Once the dams are fully open, the MNRF does not have the ability to increase the rate of flow, as it is then based on the amount of water in the system and the natural rate of flow and elevation as it moves through the wide-open dam sluice ways. To the extent possible, the MNRF operates dams to maintain water levels within the ranges identified in the established dam operating plan. For the Muskoka River, these ranges were formalized in the Muskoka River Water Management Plan in 2006. The range of operations is based on a range of factors, including recreational and environmental considerations. The plan applies to normal water conditions, while there is recognition that unusually high rainfall or snowmelt can result in high water and flooding. Water Management Plans can help regulate flows to ensure that one activity does not take primacy over another (e.g. waterpower generation over recreational use); however, they do not and cannot prevent flooding. The goal of water management planning, in the context of Section 23 of the Lakes and Rivers Improvement Act, is to contribute to the environmental, social and economic well being of the people of Ontario through the sustainable development of waterpower resources, and to manage these resources in an ecologically sustainable way for the benefit of present and future generations. The management of floods and flooding is not explicitly a goal of water management planning, and Water Management Plans are not designed to manage floods.
Floodplain mapping for most of the area was originally completed in the late 1980s and early 1990s under the Canada-Ontario Flood Damage Reduction Program (FDRP). Areas mapped include the Big East River in Huntsville and the Muskoka River, including the major lakes in the Muskoka River Watershed. This exercise identified that a considerable number of cottages and associated docks and boathouses were located within the floodplain of rivers and lakes. In the intervening time since these studies were undertaken, development in the area, particularly related to recreational properties, has increased dramatically. Recommendations included in FDRP mapping reports from the late 1980s and early 1990s include vertical water levels and horizontal setback criteria to give potential developers a choice in floodproofing criteria: either 1) build dwellings above a minimum vertical water level described in a table; or 2) build dwellings beyond a horizontal setback, also described in a table within the report. Further, this included recommendations that no encroachment be allowed where the depth of flooding during the regulatory event would exceed 1.0 metres, and no encroachment be allowed within 20 metres of either riverbank. More explicitly, the FDRP program, which focused on the identification of high flood risk designated areas in the province, included strong policies to encourage the authority, where the zoning authority is neither provincial or federal, to impose land use restrictions that will prohibit all further projects in a designated area that are vulnerable to flood damage. Furthermore, assistance under any federal or provincial disaster assistance program shall not extend to costs or losses incurred as a result of a flood with respect to any project commenced or any moveable property placed within an area after its designation or interim designation as a flood risk area. The District Municipality of Muskoka is in the process of updating its floodplain mapping using matched funding from the Federal National Disaster Mitigation Program. It must be emphasised that such mapping only adds value when used to inform development, with the intention of keeping people and property out of the floodplain. The available information suggests that land use planning and development approvals have not been proceeding in this fashion, particularly within the Township of Muskoka Lakes, which has seen significant numbers of boathouses constructed every year. For instance, between 2013 and 2016, the Township of Muskoka Lakes issued building permits for 267 new boathouses with a total value of construction of $46,263,584. As boathouses are situated atop the water, at or near the high-water mark, boathouses are always within the floodplain (or floodway) and add to the impacts during a high-water event. There is significant concern that the construction of new boathouses within Muskoka Lakes are being approved without regard for the potential damage from flood and ice heaving. Designs presented to Council include first floor plans with utility rooms, games rooms, elevators and washrooms, which are much more than a basic boathouse, and there appears to be no direction or regard for incorporating floodproofing measures into the construction plans. As these structures continue to be built in harm’s way, flooding and ice damage will only increase as will costs associated with the inevitable damage from these natural phenomena. It is unreasonable to expect that water levels can be controlled within a finite range and be kept below the damage level of docks and boathouses, or other structures, when dealing with a large river system with limited means to mitigate the magnitude and extent of flooding. With a changing climate, damages to these boathouses and other infrastructure in the floodplain as a result of flooding and ice movement will continue to occur, and most likely at increased frequency. It is not a question of if these lakes and river systems will flood again, it is only a question of when.
The Muskoka River Watershed has experienced flooding on numerous occasions in the past, including in 1976, 1980, 1985, 1998, 2008, 2013 and most recently, in 2019. Throughout the winter, MNRF staff monitor snowpack across the Muskoka River watershed to determine snow depths and snow water equivalents at which time they also evaluate soil conditions. During winter/spring 2018/2019, as in other years, the MNRF monitored the snowpack beginning in December and over the winter. In anticipation of the snowmelt and spring rainfall, the MNRF commenced the drawdown of lakes within the watershed in late fall 2018 and continued through the winter to help mitigate runoff. At this time, the MNRF took an aggressive approach, targeting the lower limit of the operating zone for the lakes. Over the winter, the MNRF continued to monitor weather conditions. To help mitigate the anticipated spring runoff, the MNRF continued to draw down water levels at the dams. There were several rain events that caused water levels to rise over the winter period and the MNRF took measures to continue the drawdown. Lake Muskoka was drawn down to one of its lowest levels in preparation for the rain, snowmelt and warmer weather expected through April. Complaints from the public about low water levels were received in late March 2019. By mid-March, the amount of water contained within a snowpack in the Muskoka River watershed was on average 171 millimetres, which is above average for this time of year but not as high as in some prior years. It is important to highlight that above average snow water equivalent does not mean flooding will occur and is one of many factors that water managers must consider when making decisions related to water management. By the beginning of April, the snow water equivalent in the snowpack had increased to 192 millimetres, representing 208% of average, with an average snowpack depth of 66 centimetres and depths exceeding 80 centimetres in the upper headwaters of the watershed within Algonquin Provincial Park. The snow survey conducted on April 15 showed that the snowpack depth had been reduced by approximately one-third (to 43 centimetres) with an average snow water equivalent of 134 millimetres, representing 148.5% of the historic average. The Muskoka Airport weather station received 129.5 millimetres of precipitation in the month of April, exceeding the monthly average by 164%. Temperatures in April were lower than the long-term average for the month, affected by values considerably lower than average for a little over the first half of the month. Notable increases in maximum temperature on April 7 (12.2 degrees Celsius) and April 12 (14.5 degrees Celsius) accompanied by overnight temperatures above 0 degrees Celsius were important in increasing runoff and sustaining snowmelt and runoff generation. Water levels on Lake Muskoka began to rise on April 7 with the warmer weather and melting snow, as runoff entered the river system. (Once inflows to the lakes are more than the maximum capacity of the dams, with all logs out, water levels will rise.) From April 10 through April 23, daily average temperatures exceeding 5 degrees Celsius and maximum temperatures ranging from 8.3 to 17.2 degrees Celsius, combined with overnight temperatures above 0 degrees Celsius, were important in sustaining runoff increases, particularly when combined with the 114 millimetres of rainfall that was recorded in the latter half of the month. The existing snowpack and associated snow water equivalents present at the middle of the month, combined with the significant rain on snow, moved considerable water volumes to rivers and lakes draining these areas. On April 17, Parry Sound District MNRF issued a Flood Watch that was upgraded to a Flood Warning on April 19, given the significant rainfall (60 to 70 millimetres), temperature increases and snowmelt that had occurred in the intervening period. Between April 7 and April 28, water levels on Lake Muskoka rose by 1.59 metres, eventually peaking on May 3. Flows in the north and south branches of the Muskoka River peaked on April 26 and April 29, experiencing the highest flows on record. Actions taken to operate the dams in spring 2019 were consistent with the Muskoka River Water Management Plan, including specific triggers to further draw down water levels when snow water content is high. Specifically, March 15 and April 1 are the key dates identified in the plan.
We hope that if you have made it this far, our Economic Snapshot has been of value to you. Please feel free to let us know your thoughts on the flooding, and the review.
