The impacts of a major hurricane on residential real estate can be devastating. Hurricane Sandy in New York City (NYC) is among the examples of how flooding can unexpectedly extend beyond FEMA flood zones. Such surprises or negative shocks can provide property owners—especially those not flooded—with new information about future flood risks, based on the difference of the property distance from the mapped flood zone and the distance to the actual locations of flooding. We use a difference-in-differences approach to quantify the effects of these shocks on residential property values for non-flooded NYC properties after Sandy. The short-run negative “surprise” effect was to lower NYC housing prices by about 6%–7% for each mile (or about 2% per standard deviation) difference between the property distance from the flood zone and the distance to the actual locations of flooding. The corresponding positive “surprise” effect is insignificant. The long-term surprise effects of flood risk on housing prices tend to disappear, as residents’ memories of the surprise fade and they seem to only recall the actual storm surge several years after the hurricane.

一场大飓风对住宅房地产的影响可能是毁灭性的。纽约市 (NYC) 的飓风桑迪是洪水如何意外扩展到 FEMA 洪水区之外的例子之一。这种意外或负面冲击可以为业主——尤其是那些没有被洪水淹没的业主——提供有关未来洪水风险的新信息，这取决于物业与绘制的洪水区的距离和与实际洪水位置的距离。我们使用差异中的差异方法来量化这些冲击对桑迪之后未淹没的纽约市房产的住宅房产价值的影响。短期的负面“意外”效应是使纽约市房价每英里（或每个标准差约 2%）与洪水区的距离与实际位置的距离之间的差异降低约 6%–7%的洪水。相应的积极“惊喜”效应是微不足道的。洪水风险对房价的长期意外影响往往会消失，因为居民对意外的记忆逐渐淡化，他们似乎只记得飓风过后几年的实际风暴潮。