Lower Thames Valley Conservation Authority is completing a flooding study jointly with the Municipality of Chatham-Kent. This study will examine flooding in the area from the Thames River Outlet at Lake St. Clair upstream to Bloomfield Road at the south-western edge of Chatham. Within this area are some built up sections, but it has mainly rural areas along the Thames River. Included in the built up areas are the local communities of Lighthouse Cove, Prairie Siding, Jeannettes Creek and Bradleyville. Urbanization continues to increase with infilling of existing lots along the Thames River downstream of Chatham. The significant number of houses built adjacent to the river and behind the diking is a concern for flood forecasting and warning staff and emergency responders. The possibility of dike failure is very real and for instance it happened in 2019. Work will include analyses that will allow the consideration of alternative planning solution for areas behind diking systems.

Moreover, the flood line mapping of the lower Thames River floodplains has not been done in over 30 years even though significant growth has occurred in this period. With up to date floodplain mapping and new policies, there is a significant opportunity for safe growth and development in the area. Existing and new development/infrastructure will be properly protected and will be designed to ensure maximum life cycling. The Thames River through the study area can be considered to have 3 distinct sections. The first section is composed of the unprotected area of the community of Lighthouse Cove in the Municipality of Lakeshore. Upstream of the community, the river is protected by diking for approximately 16 km. From the upstream end of the diking up to the city of Chatham, the river banks have no systematic flood protection. As part of the study, frequency analysis will be undertaken and a hydrologic model of the Thames River may be created to determine river flows for the study. A hydraulic model for the Thames River through the study area will be constructed. Floodplain mapping will be conducted in the area from Bloomfield Road down through the diking. Floodplain mapping will not be undertaken for the community of Lighthouse Cove. When determining flood prone areas through the diked portion of the river, it is unclear whether the Regulatory flows will be contained within the diking. Historical reports suggest that the diked portion of the river will have the regulatory flows contained within the diking. However, a preliminary hydraulic analysis suggests that the diking is likely overtopped over most of its length at regulatory flows. While there have certainly been instances where the dikes have been overtopped due to ice jams, this study will begin by examining locations where the dikes may be overtopped or breached during free-flow conditions and undertaking floodplain mapping for those areas behind the diking subject to such flooding. Since the community of Lighthouse Cove has only ever experienced riverine flooding under ice jam conditions, it is not clear if the community would flood under free flowing Regulatory flows. If it is discovered that the community is susceptible to free flow riverine flooding through this study, model outputs that could be used for floodplain mapping will be included in the project deliverables. However, flood line mapping will not be prepared for Lighthouse Cove as part of the study.

Recommendations will be made that will lead to addressing risk management issues and potential for growth adjacent to dikes including spill areas that would result from dike failures. The latest technology will be used to create a high-resolution map of the area that will permit communities to plan with updated floodplain information. Information from this study will be included in the proposed Official Plan update for the Municipality of Chatham-Kent. The data captured can additionally then be used as an important data set for the Municipality’s Geographic Information Systems. The gathering of this new information will facilitate the review of new development projects including infrastructure planning and sound land use planning.