Projected Sea Level Change

Transcription

1 UBCM 2011 RISING OCEANS & RAISING DIKES A LOCAL GOVERNMENT PERSPECTIVE Carrie Baron, P.Eng. Drainage & Environment Manager Projected Sea Level Change Provincial Government reports predict sea level changes for BC. Key factors included in these reports are: Sea level rise projections 2100 & 2200 Ocean surge Wave run-up Vertical Land Movement Land Subsidence 1

2 2100 PredicHons Predictions are 100 years in the future but as the a community redevelops and infrastructure is renewed, these factors need to be considered in designs. Planning for the Change Knowing when systems need to be redesigned for Sea level rise is important. when will my dikes start being over topped? when do roads or bridges need to be raised? do homes have to be built differently in an area? Over what time period? Most communities have 10 year plans and are developing plans for asset renewal on longer terms. Knowing how the changing water levels impact a community are critical to overall planning. 2

3 A 1 to 2 meter sea level rise in Boundary Bay may be felt throughout the Serpentine, Nicomekl & Little Campbell River floodplains and into historic urban development areas. Dikes as Protection New sea levels may mean raising existing dikes or constructing new dikes to protect new floodplain areas. There is more than just building a dike to flood protect an area 3

4 Behind the Dike Impacts Areas behind the dikes are isolated and may not be able to freely drain. Lands in the floodplain may now flood to higher levels, for longer periods of time and more frequently Some factors which need to be considered include: Construction elevations for buildings and infrastructure Pump stations for conveyance of rainwater Storage & conveyance for rainwater to flood boxes & pump stations Groundwater levels Salt water intrusion & its affect on infrastructure, agriculture & vegetation Land Use Planning Floodplain changes will necessitate looking at zoning issues such as: exishng developing policy on development in floodplains taking into consideration future water levels setting of flood elevations existing building criteria possible marine buffers / setback areas infill or rebuild situations where variable land and building heights are present 4

5 Pump stations Diked floodplain areas require pump stations to operate at times of high river or sea levels. Pump stations draw down the water quickly, thus often need forebay storage area for water to pool and debris to be trapped Groundwater Influence In some areas, rising ocean levels can influence groundwater keeping these levels in floodplain areas high. Some strategies for flood protection will require managing groundwater. Care will need to be taken on how this is done as it can lead to land subsidence or changes in the salt water wedge in an area. Salt water can significantly affect underground utilities. 5

6 Tidal Influence on Groundwater Infrastructure considerations Placement of infrastructure in the floodplain area is critical. Some key items include: Sanitary lift stations (and treatment plants) Electrical control boxes for traffic signals and street lights Key potable water infrastructure (prevention of backflow) Access roads to pump stations and other critical infrastructure Emergency access 6

7 Beyond a Local Government s Control In addition to local government infrastructure within the floodplain, many private and senior government agencies own and operate infrastructure within the floodplain. These agencies and assets include: Highways constructed across floodplain areas Agricultural Land Commission Port facilities Railway facilities and tracks along shorelines and through floodplains BC Hydro, Fortis, Kinder Morgan, Shaw, Telus etc. who have critical infrastructure in & across floodplains Treatment plants, transmission lines i.e. Metro Vancouver facilities in floodplains Assistance at all Phases As communities begin to examine what the new provincial documents could mean to them, they will quickly find they will need expert resources, cooperation from other levels of government and financial assistance. The base planning studies to find out impacts could be expensive Conducting designs, acquiring properties, getting approvals from fisheries and others will be complicated and expensive Implementing design features which include more than just dike construction will be a challenge as existing flood funding is targeted for dykes and some pump stations typically. Having Fisheries and Oceans (DFO), Environment Canada and Water Act waive some of the environmental requirements will be critical as shoreline squeeze will occur. Changing provincial policies regarding local government liability i.e. flood construction elevations or non conforming dikes is necessary 7

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