Context
On July 8, 2013, a storm occurred that produced Toronto’s record rainfall in a day. The precipitation mechanism resulting in the downpour involved the advection of a weak low-pressure system and a mass of warm and humid air, which made its way over Ontario (Boodoo et al., 2015). The advection developed into several short-lived, pulse-type thunderstorms. However, these storms were not accompanied by any damaging winds or hail (Sandink, 2016). They were only characterized by heavy rain, which fell across Southern Ontario to cause significant flash floods. The mid-afternoon saw the development of a weak surface pressure trough in the north of Toronto. The high humidity resulted from the proximity to Lake Ontario and Lake Erie. The conditions were an indication of highly precipitable water, weak winds, and weak shear.
Normally, moisture, instability, and lifting are required for the development of a convectional storm. Apart from these three components, Boodoo et al. (2015) mention wind shear as the fourth component that produces severe thunderstorms. The surface dew point must also be at least 55 degrees Fahrenheit to trigger a surface-based thunderstorm. The type of convective precipitation which occurred in Toronto was caused by both lifting and instability. In this case, air rose on its own after being lifted to the troposphere. According to Park and Min (2017), instability makes air to rise faster compared to the case of forced lifting alone. During these processes, there was an increase in relative humidity due to a subsequent rise of unsaturated air. Upon saturation, the lifting produced clouds, hence precipitation. As a result, there was thunder and heavy precipitation of almost 140 mm which lasted just two hours.
Surface and Groundwater Hydrology
Land cover under the management of Toronto and Region Conservation Authority ranges from mostly rural areas to large urbanized cities, in this case, the Don River Watershed. According to the Toronto and Region Conservation (2009) report, groundwater hydrology in these watersheds is affected by the physiography on the surface and underneath the waterfront. Urbanization poses the greatest challenge to the watershed within the TRCA Region. In this regard, urbanization has created an impervious cover in the watershed, which limits the natural infiltration of precipitation. The effects of the impervious cover caused by urbanization are evident in Mansoor et al.’s (2018) comparison of the rivers’ stream hydrographs. Artificial pipes and channels have, therefore, been used to direct rainwater straight to the watercourse.
The tributaries of Don River West were piped and buried after the reclamation of wetlands. It means that the hydrologic cycle of the watershed was altered by the expanses of roads, parking lots, rooftops, pavements, and gutters (Mansoor et al., 2018). During extreme storm events, the water which once soaked into the ground is currently collected in interconnected underground sewers and taken to the river. However, urban flooding, which is directly linked to heavy precipitation, has been on the rise in the region. In response to this, TRCA implements projects such as natural landscapes for absorbing and collection ponds for holding back runoff (Toronto and Region Conservation, 2009). However, such projects only manage small to medium stormwater.
Flood Management in Urban Settings
Impacts of Flooding in Highly Urbanized Cities like Toronto
Storm events cause problems associated with urban flooding, especially when the floodwaters overwhelm cities’ sewer systems and flood low roadways and underpasses. Homeowners also cope with losses in terms of irreplaceable damage by the floods and basement flood damages which reduce the liveability of homes (Jha et al., 2012). This especially occurs when homes flood with raw sewage. Water damage due to failed household plumbing systems has been a significant reason behind many insurance claims in Canada (Sandink, 2016). It, therefore, portrays the extent of anticipated losses due to flooding in highly urbanized cities.
Apart from damage to infrastructure, flooding in highly urbanized cities produces health effects linked with dampness and growth of mold which have become common, especially when there is a recurrence of flooding. The fact that floodwaters are directed to sewage lines result in disease transmission through fecal-oral contamination (Sandink, 2016). This occurs when floodwaters containing sewage material contaminate building materials, therefore facilitating the growth of human pathogens. Jha et al. (2012) also mention that flood events in highly urbanized cities have implications for local governments. Toronto, for example, experienced losses in terms of operational and capital costs following the flood event. Local governments are also prone to facing lawsuits from residents being affected by sewer problems.
The Role of Policymakers in Terms of Emergency Preparedness
Flood risk mitigation and response form the basis of policy development. It included identifying the hazard, assessing the potential impacts of the hazard, and coming up with strategies to manage current and anticipated flood events. Policymakers address the increasing stresses subjected to watercourses (Toronto and Region Conservation, 2009). With the continued sprawl of cities, policymakers have come to acknowledge that flooding will is bound to become a significant risk. Moving into the future, they continue working to adapt to new flood management strategies. In Ontario, for example, it has taken the joint effort of all levels of governments, TRCA, non-governmental organizations, and community members to reduce risk and manage flooding events (Mansoor et al., 2018). Policymakers, therefore, create more resilient cities to future floods associated with climate change.
Considering that land use has been the centre of attention when floods occur for decades, policymakers focus on the issue as an effective tool to reduce community-level risks. In this sense, policies are developed to guide how land is used in particular areas (Jha et al., 2012). In the case of cities, zoning is undertaken by multiple levels of government through the formulation of national and local policies which designate land for specific uses. Where appropriate, constructions in a particular area such as public parks are prohibited. Notably, policymakers design and implement Strategies for Flood Risk Management in fragmented settings. This includes allocating complex and resource-intensive tasks to federal governments.
Policy Recommendations
Current policy context addresses issues such as land-use planning, the protection of water bodies, maintenance of the river water quality standards, and prevention of natural hazards. However, there is yet to be legislation guiding the implementation of these initiatives at the provincial level in Ontario. It would, therefore, be necessary to establish an Act that will have a direct impact on the management of wet weather flows. Furthermore, the Act will ensure that all municipal policy documents are formulated under common legislation. There will also be consistency in the approach taken to manage flood risk across the entire province. Moreover, municipalities will be held accountable for the standards of flood risk management, which ultimately reduces flood risk.
Through an analysis of the impacts of flooding in highly urbanized cities such as Toronto, it is clear that there is a need to manage urban water cycles as a single system. This means that the province should develop a holistic systems approach that integrates all aspects of water management such as the vulnerability of water for industrial and domestic use, the effectiveness of sewerage systems, and management of floodwaters. In this sense, Toronto will form part of a larger management system encompassing all watersheds along the Don River. Having more agencies manage a natural system increases the risk of conflict and prolongs the time required to implement projects. Consolidating all the nine watersheds under the jurisdiction of the TRCA will ensure that all tasks are effectively implemented.
Lastly, Toronto needs to change how it perceives its river basins and waterfronts in its holistic approach to water management. This requires shifting from the traditional idea of flood control to adopting the thought of welcoming floodwaters. It means that the city residents and authorities must reacquaint themselves with floodwater and change their perception of it, considering that it will always shape the way they live. Risk acceptance creates room for resilience rather than resistance to flooding. The city can reduce the risks associated with flooding by accepting the existence of floods. Furthermore, the Intergovernmental Panel on Climate Change (IPCC) predicts more precipitation in Southern Ontario because of climate change. It is, therefore, upon the city and its residents to identify the social and ecological benefits of flooding. With increasing populations in Toronto, functional environments such as the Corktown Common Park to integrate civic park design while protecting against floods.
References
Boodoo, S., Hudak, D., Ryzhkov, A., Zhang, P., Donaldson, N., Sills, D., & Reid, J. (2015). Quantitative precipitation estimation from a C-band dual-polarized radar for the 8 July 2013 flood in Toronto, Canada. Journal of Hydrometeorology, 16(5), 2027-2044. Web.
Jha, A. K., Bloch, R., & Lamond, J. (2012). Cities and flooding: A guide to integrated urban flood risk management for the 21st century. The World Bank.
Mansoor, S. Z., Louie, S., Lima, A. T., Van Cappellen, P., & MacVicar, B. (2018). The spatial and temporal distribution of metals in an urban stream: A case study of the Don River in Toronto, Canada. Journal of Great Lakes Research, 44(6), 1314-1326. Web.
Park, I. H., & Min, S. K. (2017). Role of convective precipitation in the relationship between subdaily extreme precipitation and temperature. Journal of Climate, 30(23), 9527-9537. Web.
Sandink, D. (2016). Urban flooding and ground‐related homes in Canada: An overview. Journal of Flood Risk Management, 9(3), 208-223. Web.
Toronto and Region Conservation. (2009). Surface water hydrology/hydraulics and stormwater management–Report on current conditions [PDF document]. Web.