Where Mapping May Mean Devaluation
environmental monitoring, mapmaking June 11th, 2008When it comes to mapping, there’s no area more highly charged than flood or fire mapping. When determining these risks, a rigorous methodology is needed because the outcomes have great impact on the property-owner’s pocketbook. An unfavorable ruling that designates a previously risk-neutral property as an at-risk property has huge implications on the market value and insurance burden of that property.
I just read a news post from Australia where brushfire mapping has been used to classify homes that are at risk of fire. The city council of one city is fighting rulings that have classified homes near the harbor, and homes on narrow strips of land, as brushfire-prone properties.
I also read that the Federal Emergency Management Association (FEMA) is providing a 90-day flood map review process for residents of Monmouth County, New Jersey. Here residents are given 90 days to submit an appeal if they don’t believe that their flood zone classification matches the risk on their property. The residents must supply technical documentation that details risk mitigation elements such as topography or engineering measures.
I like the idea of a review period for individual property owners as it seems to be a very democratic and measured approach to the inevitable individual conflict resolution. The council’s defense of citizens is somewhat suspect, given their defense of property values for a better tax base. It’s generally federal funds that get the hit in major disasters, so the federal regulation should win out on this type of inter-governmental dispute.
With impending sea-level rise, FEMA will be quite busy with updates in coastal areas. FEMA’s Map Assistance Center handles any questions regarding rules, regulations, requirements and criteria for appealing any changes in the map. I wonder what percentage of appeals are successful?
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June 11th, 2008 at 4:42 pm
If you dig under the hood of the flood maps, it rapidly gets ugly. Essentially, we now have lovely digital FIRMS, which seem not to align well with other maps… Reason being they were digitized from paper maps. The paper maps in turn created by taking topo quads and hand-scaling a rough geometry and a handful of cross-sections, and running them through HEC, to get a water surface profile for a statistical flood event. So there’s a lot of fine detail that ends up getting lost, but worse yet, there’s become a complete disconnect between the process and the maps. Layer on top of this the piecemeal LOMA process, which deals in base flood elevations and other things which might not completely be valid.
Most of this got put in place decades ago… Skipping forward to the present, we have much digital elevation data, such as statewide LIDAR in some cases, we have more robust and detailed statistical risk data, storm modeling capability, land use and land cover data, and detailed stream centerlines such as NHDPlus – and most importantly, we have computing horsepower which can deal with far more complex flood risk modeling than those early, crude models upon which most of our modern maps are based.
While the system was (and still is) tremendously flawed, a democratic process is not necessarily the right approach. Floods don’t honor democracies, they don’t honor human decision.