Use of Watermarks for Discerning Hurricane-Induced Flood Levels

Property damage attributable to hurricane-induced floods can be difficult to discern once flooding has subsided; however, flood levels can be estimated by measuring watermarks left by standing water on interior and exterior finishes including glass, gypsum board, exterior siding, fences, landscaping, etc. This paper illustrates how field measurements of watermarks can be used reliably, along with other field observations, to assess structure distress related to flood. A particular application of this can be seen in a dispute stemming from property damage related to Hurricane Katrina, in which the author was posed the task of determining if commonality existed to qualify for a class-action lawsuit. During site visits to putative class properties in the city of New Orleans, watermarks were field-measured to establish an estimated flood level, and the causes of various distress to each structure were analyzed including wind and flood. The field-measured watermark data were compared to the Interagency Performance Evaluation Taskforce (IPET) reported levels and revealed good correlation. The damage attributable to flooding was then compared across properties resulting in a conclusion that each property sustained significantly differing levels of damage, including some with no flooding above the finished floor; and thus did not meet commonality.