OCR Text |
Show PART VII PROCEDURES Unit damage values were then assigned to the affected acres. For areas where data was lacking, damages were estimated by means of comparison. Factors of hydrology, land use, productivity, and economic character- istics were evaluated in making the comparisons. The 1966 Conservation Needs Inventory, which identified areas damaged by small watersheds, was a primary source of data for the non- federal lands. During the study information on the 100-year frequency flood plain areas, damageable values, and probability of flooding by month were developed. Average annual damages were based on an analysis of flood frequency curves. Determination of Average Annual Damages Resulting from Upstream Watershed Problems Projected Without Upstream Watershed Treatment The estimated future upstream damages are for the Framework Plan, Regional Interpretation of OBERS projections, without additional land treatment or upstream flood protection works. The projected production expressed in units or dollars in Appendix VI, Land Resources and Use, illustrates the potential development in the future and were utilized in projecting upstream damages. The present damage in relation to the present productivity was considered in projecting future damages. Determination of Costs of Watershed Treatment Projected to 2020 A unit cost based on past installation costs in the region was applied to each practice or measure on Table 16. Overhead costs were included in the unit cost and were based on the difficulty of installing a practice or measure. Nonstructural treatments required less overhead than structural measures on a per unit basis. Operation, maintenance, and replacement costs were based on the length of life of the structure or nonstructural treatment and durability of the measure. These costs are an annual cost for the last year of the time frame. 86 |