water within the protection area which are subject to an indeter- 

 minate combination of wind, waves, and tidej and (3) losses to 

 shellfish beds which are disturbed or contaminated. Losses such as 

 these have been omitted from the economic analysis, because they 

 consist of damans to items which are not always present in the 

 same place, at the same time, or in the same quantity. To put 

 losses in this category in perspective for analysis would require a 

 framework of multiple assumptions. 



The following paragraohs describe the economic and physical 

 changes, in addition to price level changes, which are reflected in 

 the computation of recurring flood losses, 



b . Evaluation of individual flood-protection measures . The 

 stage-loss relationship reflects an evaluation of the effectiveness 

 of permanent and semi-permanent flood protection devices and meas- 

 ures where they have been installed since the hurricane of 195U at 

 industrial concerns, commercial houses, and public buildings. These 

 protective measures include permanent closure of windows and other 

 openings, provision for closure of discharge lines, extension and 

 reinforcement of walls, construction of flood walls, installation of 

 pumps to control seepage and interior runoff, evacuation of plant 

 storage space susceptible to flooding, and the organization of flood 

 plans to put semi -permanent closures and evacuation of vulnerable 

 space into effect. Credit for these types of individual protection 

 measures has been assumed to influence the stage-loss relationship 

 to a stage one foot below that of 195U, 



Credit for local protection measures to the full 195U stage was 

 not considered reasonable because of the weaknesses inherent in this 

 kind of protection and the many unknotflns involved in local flood- 

 protection problems. These unpredictable factors include (l) the 

 vulnerability of both walls and floors to the hydrostatic pressure 

 created by flooding of the 195U magnitude j (2) the possibility of 

 overtopping by hurricane flood peaks j and (3) the danger of a break- 

 through under the battering of wind-driven debris, which would per- 

 mit salt water to enter and thereby 'nullify all other protective 

 measures. 



In addition to the possibilities of physical failure, the ef- 

 fectiveness of plant protection is further weakened by the critical 

 importance of the time element involved in putting flood plans into 

 operation. Owing to the heavy non-recoverable losses incurred by a 

 complete plant shutdown, concerns are reluctant to put their plans 

 into total operation until dar^erous flooding is iminent. Consider- 

 ing the vagaries of hurricane movements and warning systems, this 

 delay can be disastrous, Optiraxun conditions, including a sufficiently 

 early hurricane .flood warning at a time when adequate numbers of per- 



D-n 



