What are Natural Hazards?

There are a number of natural physical processes that can produce unexpected events which can be catastrophic and result in damage to property, injury to people and occasionally, loss of life. These processes are considered natural hazards. Within the Otonabee Conservation watershed, natural hazards of particular concern are flooding hazards, erosion hazards and unstable soil or bedrock.

Flooding of river or stream systems can occur at any time, including following a spring freshet or extreme weather events rainfalls. During a flood, river or stream levels rise resulting in the inundation of areas not ordinarily covered by water. There areas are known as floodplains. Rivers and streams naturally accommodate flooding in their valleys; the floodplain is really part of the river or streams natural living space.

River and stream systems (including all watercourses, river, streams and inland lakes) are by nature dynamic, constantly changing landforms mainly due to erosive forces or flowing water and the relative stability of surrounding slopes. The constant shaping and re-shaping of river and stream systems associated with flooding, erosion and slope instability result in the creation of hazardous conditions that can pose a threat. The erosion hazard associated with river and stream systems is that area of a river or stream banks and areas adjacent to watercourses where erosion is actively occurring and/or where development could create slope stability issues.

Unstable soils include organic soils which are typically associated with wetlands. Organic and peat soils are formed by the decomposition of vegetative and organic soils into humus which can release humic acid in the ground and create highly combustible methane gas. These soils also lack soil structure, making them susceptible to erosion and are unable to support buildings and structures because they compress so easily.

Understanding Natural Hazards

How are Conservation Authorities involved in Natural Hazards Management?

Prevention – Providing flood risk information to municipal planners and the general public to promote proper land use planning and regulation of new and existing development on flood plains thus preventing or reducing flood risks to people from living and/or working in flood prone areas.

Protection – In order to protect against flooding, CAs have constructed and maintain protective infrastructure such as dams and dykes or purchased lands located in hazardous areas. In the past, both the provincial and federal governments have contributed to these projects.

Emergency Preparedness and Response – It is imperative that existing flood risks are understood and that floods are forecasted to the extent possible. Understanding flood risk and providing advance warnings is critical to allow municipalities to prepare and implement plans which allow quick response to emergency situations created by flooding.

Conservation Authorities are responsible for monitoring and predicting flood flows and water levels within their watersheds, operating flood control structures such as dams and disseminating flood messages to local municipalities and agencies.

Conservation Authorities work closely with the Ontario Ministry of Natural Resources and Environment Canada to provide advice to municipalities in the preparation of flood contingency plans and during the emergency response process.

Conservation Authorities and the Ontario Ministry of Natural Resources use information gathered from stream gauges, weather stations, snow surveys, meteorological forecasts and computer models to forecast potential floods.

Programs and services to prevent and control flooding offered by Conservation Authorities include

  • monitoring conditions;
  • computer modeling and forecasting flooding;
  • issuing of flood messages;
  • regulation of development in flood prone areas;
  • providing planning support and advice to municipalities to minimize the impact of flooding;
  • land acquisition;
  • protecting significant ecosystems such as wetlands and forests that help to control flooding; and
    educating the public.

Good land use planning and the regulation of hazardous lands and unsafe development is a prevention measure that is used to lessen the risk to loss of life and minimize property damage. During the planning or permit process, the delineation of a floodplain or the extent of an erosion hazards many be required. Any such studies need to be done in accordance with the following provincial guidelines by a qualified professional:

  • Technical Guide, River & Stream Systems: Flooding Hazard Limit
  • Technical Guide, River & Stream Systems: Erosion Hazard Limit

These documents are designed for use by technical professionals and can be obtained from the Institute for Watershed Science