2.4.16 Evaluation procedure: Data sources. 



The following summarizes problems associated 

 with two key data sources: 



(a) Interviews. The primary use of personal inter- 

 views is to collect flood damage data, but inter- 

 views may also be used to collect other necessary 

 data not available from secondary sources. Use 

 only interview forms approved by the Office of 

 Management and Budget. Use statistically sound 

 techniques for selecting the interview sample and 

 for devising the questions. The questionnaire and a 

 summary of responses should be compiled and dis- 

 played in the final report in a way that protects the 

 source of individual disclosures. Describe the errors 

 and uncertainty inherent in the sampling methods 

 and responses. 



(b) Local land use plans. Local land use plans 

 and zoning ordinances are valuable guides to future 

 land use in the floodplain, but caution must be ex- 

 ercised in the use of such plans and ordinances. 

 First, the demographic implications of local plans 

 and ordinances must be consistent with, or con- 

 vincingly distinguished from, trends in a larger area, 

 e.g., OBERS. Second, a local plan is not an accept- 

 able projection for the without-project condition if it 

 ignores the flood hazard. Third, the status, date, 

 and likelihood of change of local plans vary. Finally, 

 local plans may not contain sufficiently detailed in- 

 formation to be of direct use in benefit analysis. 



2.4.17 Report and display procedures. 



Include in the report enough data to enable the 

 reviewer to follow the key steps above and, more 

 important, the underlying rationale for the project. 



(a) Report procedures for risk and uncertainty. To 

 assist reviewers in assessing response to risk, sum- 

 marize the following separately and display the in- 

 formation in tabular form: 



(1) Remaining flood damage situations: Categori- 

 zations. The remaining damages are those expect- 

 ed to occur even with a floodplain management 

 plan in operation. Remaining damages include: 



(i) Damages to activities that would occupy the 

 floodplain with as well as without the plan; 



(ii) Damages to activities that would occupy the 

 floodplain only with the plan; and 



(iii) Increased damages to activities outside the 

 protected area with and without the plan. This in- 

 cludes downstream flooding, if any, caused by the 

 plan or project. 



(2) Flood with two-tenths of 1 percent chance of 

 occurrence. Fully describe the flood with two-tenths 

 of 1 percent chance of occurrence (500-year fre- 



quency) with and without the plan. The report 

 should contain, for example, two-tenths of 1 per- 

 cent flood damages; the number of people and 

 towns affected; the number of structures and acres 

 by land-use type; disruption of essential services 

 (e.g., water, power, fire protection, and sanitary 

 services) and distance to unaffected essential serv- 

 ices; anticipated warning time; flood depths, veloc- 

 ity, duration, debris content, etc.; and other indica- 

 tors pertinent to catastrophic flooding. 



(b) Summary tables. Summary tables 2.4.17-1 

 through 4 are suggested presentations for all re- 

 ports that include flood hazard reduction as a pur- 

 pose. Other summary tables, such as the displays 

 presented in 2.4.5 through 2.4.15, may be neces- 

 sary and pertinent. The summary tables should in- 

 clude pertinent land use data for computing not 

 only NED benefits, but also environmental, social, 

 and regional impacts. Also present other floodplain 

 data pertinent to the evaluation on one or more 

 maps: Flood limits and depths with and without the 

 project; current and future land use; and 100-year 

 and other flood limits and depths. 



Table 2.4.17-1— Summary of Annualized NED 

 Benefits and Costs for Alternative Projects 



[Applicable discount rate: ] 



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40 



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