This post is the first in a series that describes the state of flood hazard mapping in British Columbia. If this piques your interest you can also check out:
Flood hazard maps are a basic tool. Without a good understanding of where and how deep water might be in a flood event, we’ve no hope of making sound decisions that will mitigate our losses down the road. Internationally, flood maps are recognised a necessary starting point for flood management 1, and have recently been shown to have a return on investment of 2:12.
So, with the knowledge that flood maps are important and valuable we’ve decided to delve into the coverage of mapping in BC. The Federal Government recently commissioned a study to look at coverages nationally, where it was reported that 2,656 km of rivers have been mapped in BC, but that this is less than 50% of what needs to be mapped3. The authors also note that the mapping in the province is old and out-of-date. This study is a great starting point, but doesn’t go deep into the data.
So, in order to get a conversation rolling locally, and let’s be honest – some more mapping completed in the province – the Ebbwater staffers set ourselves the task of building a GIS database of existing mapping in the province. As our starting point we used the Province of BC dataset, but because we were interested in more than just what areas had been mapped, we also spent many hours trawling through the original documentation and metadata to record:
- The age of the map
- The return periods mapped
- The methods used to establish the design flows, along with the length of record of any hydrometric data
- The methods and models used for hydraulic calculations, including details on the collection of bathymetric data.
- The inclusion/exclusion of any reference to climate change
Quite simply it is not a pretty picture. As a starting point, we’ve looked at the age of maps in the province – based purely on when the map was released (not on other important factors like when the hydrologic calculations were actually done, or when a river was actually surveyed – we’ll save those tidbits for another post).
The chart clearly shows that our maps are old. All of the provincially designated maps are more than 15 years old, and have a median age of 26 years. Unfortunately, it matters that the maps are old. Flood maps are not static, and should be updated regularly because the underlying data that informs them (the climate, the hydrology (the volume of water), the geomorphology (the shape of the river) and the land use are constantly changing). This on top of the fact that the technology has changed dramatically in the last few decades and of course we are now dealing with a non-stationary climate. Maps need to be updated regularly to capture these changes and to be useful. The U.S. FEMA Risk Map project suggests that maps should be reviewed every 5 years at a minimum4. None of the provincially designated maps comes even close…some of our maps are almost 4 decades old.
Clearly we have a lot of work to do, but with some support from all stakeholders (government, large asset holders, floodplain residents) and the attitude that one new map is better than no new maps we can chip away at the problem.
February 2015 update: We’ve done a little extra work on the BC Flood Map Project – check out our next post on the map coverage in BC here.
The Ebbwater BC Flood Map Project
We’ve just started our gap analysis and thought project on flood maps in BC and have a whole host of other analyses that we want to complete. We’d love to hear from you if you have a good idea on how to use or present the data, we’d also love to hear from you if you know of or have a map that’s not in our database – we’ve started our project using the Province of BC dataset, but know there are other maps (newer and better ones!) out there and would like to include them. You can contact us by email: BCFloodMapProject@ebbwater.ca or feel free to call or drop by our office.
This post is part of Ebbwater’s portfolio of Pet Projects. If it has piqued your interest, why not check out some of our other posts.
- Associated Programme on Flood Management. Integrated Flood Management Tools Series: Flood Mapping.; 2013.
- The Association of State Floodplain Managers. Flood Mapping for the Nation: A Cost Analysis for the Nation’s Flood Map Inventory.; 2013:1-15. http://www.floods.org/ace-files/documentlibrary/2012_NFIP_Reform/Flood_Mapping_for_the_Nation_ASFPM_Report_3-1-2013.pdf.
- MMM Group, JFSA, Matrix Solutions Inc. National Floodplain Mapping Assessment Final Report.; 2014.
- FEMA. FEDERAL INSURANCE AND MITIGATION ADMINISTRATION POLICY FP 204-078-1 (Rev 2).; 2014:1-92.