Google Earth Community: FEMA National Flood Hazard Layer

First, many thanks for posting a link to the FEMA data that is dramatically more usable than FEMA's MSC Viewer:) It even works fairly well over a satellite internet connection (AKA the last resort for bandwidth in the boonies). The 'seamlessness' of the data is very welcome for those of us with property that spans a FEMA FIRM map boundary.

Unfortunately this link also makes it very easy to see the small spatial flaws in the FEMA FIRM maps when compared to aerial photo montages (e.g. Google earth). For example, creek centerlines that do not stay within a creek's normal channel; flood hazard zones that do not encompass the full width of damed sections of a creek; and flood hazard zones that wander up onto hill sides near creeks.

At first I thought these small spatial flaws were due to spatial errors in Google Earth's aerial image montage. But nearly identical spatial flaws are visible via FEMA's own MSC Viewer. On our property these spatial errors are on the order of 50'-100'. This is a really good fit for a 'national' data set. But if taken literally could unnecessarily restrict building on one side of a creek (or river), while allowing much riskier construction on the other side.

It would help if the FEMA overlays included "landmarks" that are easily recognized in an aerial photo montage (e.g. road intersections). This would allow people to better judge the spatial fit to the land and make more informed decisions prior to building.

Talon Dancer

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