Comments on: Where Mapping May Mean Devaluation http://www.vector1media.com/spatialsustain/where-mapping-may-mean-devaluation.html Promoting Spatial Design for a Sustainable Tomorrow Wed, 08 Feb 2012 13:39:33 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Dave Smith http://www.vector1media.com/spatialsustain/where-mapping-may-mean-devaluation.html/comment-page-1#comment-4142 Dave Smith Wed, 11 Jun 2008 22:42:47 +0000 http://vector1media.com/spatialsustain/?p=761#comment-4142 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. 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.

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