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 Flood Forecasting and Warning System
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72 Hours Get Prepared


The Central .Lake Ontario Conservation Authority maintains a flood forecasting and warning system. The purpose of the system is to reduce risk to life and damage to property by providing local agencies and the public with advanced notice, information and advice so that they can respond to potential flooding and flood emergencies.

Flooding in Ontario is a fairly common occurrence. The most severe flooding on record in Ontario occurred in October 1954 when Hurricane Hazel passed through the Toronto area. Hurricanes are not the only type of event that can cause flooding. Heavy spring rains and snowmelt commonly result in flooding, particularly in larger watersheds. High local rainfall associated with severe thunderstorms can cause flooding usually associated with smaller watersheds. Winter ice jams associated with spring break up also has resulted in severe flooding situations. High great lake levels and/or storm surges can also result in lakeshore flooding.

Flood Forecasting & Warning
Flooded house 1980 - pumping basement Photo: CLOCA



The Central Lake Ontario Conservation Authority monitors, on an ongoing basis, weather forecasts and watershed conditions at locations across the watershed. Water level and related information is recorded through an extensive network of stream gauges, rain gauges, snow course sites and staff gauges (monitoring network). These measurements, weather forecasts and radar information on temperatures and rainfall predictions, along with historic data, are all taken into consideration when developing a flood forecast.

When spring melt or severe storms are anticipated, the Conservation Authority estimates the severity, location, and timing of possible flooding, and provides these forecasts to local agencies.

 Forecasting and Mapping Products

As a service to our municipal and regional partners and our watershed residents, CLOCA has developed the following web sites that will provide information regarding floodplain limits, structures and roads in flood damage centres

The Hydrologic Information System (HIS) is a geographically distributed network of hydrologic data sources and functions that are integrated using web services so that they function as a connected whole. The data hosted on this server have been published using the Consortium of Universities for the Advancement of Hydrologic Science, Inc. Hydrologic Information System The goals of the HIS Project are to make hydrologic information universally accessible and useful, and to provide access to the data sources, tools and models that enable the synthesis, visualization and evaluation of the behavior of hydrologic systems. The CUAHSI HIS website contains tools for implementing Hydrologic Information Systems.

Flood Forecasting and Warning Common Operating Picture - Secure Access
CLOCA's Flood Forecasting and Warning Mapping Application was designed for use by the Flood Watch Team. It is accessible by CLOCA's Flood Forecasting and Warning partners and staff through a secure login. The map displays Flood Vulnerability data and real time precipitation and water level data from CLOCA's monitoring gauges. The Flood Forecasting and Warning Application also provides access to the Flood Vulnerability map sheet pdfs for download. The Flood Forecasting and Warning Mapping Application requires installation of the Microsoft Silverlight plug-in for your web browser.

Geoserver - Secure Access
Geoserver is an open-sourced software server that allows the sharing of geospatial data. CLOCA has hosted spatial datasets which the public and its partners will be able to integrate into their GIS software. For a detailed guide on connecting GeoServer with your GIS software please contact Rod Wilmot, GIS/IS Supervisor. Non-GIS users will be able to view the data without specialized software; the GeoServer webpage provides the user the ability to download KML files which are compatible with Google Earth.

 Flood Event

A flood event may be defined as a sudden increase in watercourse levels resulting from the occurrence of precipitation, snowmelt, or a combination of the two. The severity of flood events range from minor increases in creek levels (resulting in ˇ§hazardous creek conditions?, to extreme flood conditions (posing a risk to life and property). These various types of events, and the corresponding flood response activities, are described in the Flood Contingency Plan, prepared by the GTA Conservation Authorities for the Regional Municipality of Durham. A copy of this document is located in the Library section.


Be Prepared

Take steps tp protect yourself, your family and business, in the event of a flood or other emergency. Visit the following pages for more information:

  1. Emergency management Ontario
  2. Public Safety Canada
  3. Ontario Ministry of Natural Resources
  4. Durham Region


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