Orestimba Creek Feasibility Study - Stanislaus County

More documents

Recommendations

Info

Economics Appendix – Draft Report - Orestimba Creek Feasibility Study, Stanislaus County, California – September 2012 4.0 Uncertainty and Other Categories 4.1 FLO-2D Grid Cells and Parcel Assignments using GIS GIS was used to assign centroids to each parcel within the study area and these “points” were then overlaid onto the grid-cells of the FLO-2D model, resulting in the assignment of each parcel to a specific grid-cell within the hydraulic model. Due to the random nature of parcel spacing compared to the structured nature of the FLO-2D grid-cells, some grid-cells contain zero parcels and other grid-cells have multiple parcels assigned to them. The water surface elevation of the grid-cell now becomes the water surface elevation for all parcels contained therein. Using the grid-cell assignments along with the depths of flooding for the 20%, 10%, 5%, 2%, 1%, 0.5% and 0.2% ACE probability events, water surface profiles were developed and imported into FDA. 4.2 Economic Uncertainty Parameters Many of the factors that determine flood damages can be represented by a range of values instead of a single number. Errors in measurement, variation in classification and judgment can lead to differences in values. For this study, in accordance with EM 1110-2-1619, uncertainties in the following parameters were considered in the damage estimation: Structure Value Content Ratio First Floor Elevation (Foundation Height) Depth-Damage Percentage Structure values were determined as a function of Marshall& Swift values per square foot, square footage and estimated depreciation. To estimate the mean value of structures, a triangular distribution for each of these parameters were set in the model as discussed in detail in section 2.3. In addition, standard deviations for all 4 variables were used for all land use/structure types within the FDA model and applied during FDA’s Monte Carlo simulation of the Expected Annual Damages. These coefficients of variation were based upon @Risk Monte Carlo simulations for representative structures for each category as listed in Table 4-1. Risk and uncertainty was also included in the Depth Damage Percentages for residential structures and contents that were imported into FDA and applied during the Monte Carlo simulations. A summary of the standard deviations used for residential is also shown in Table 4-1. Uncertainty in non-residential content depth damages were also applied in the form of triangular distributions and the most common categories are summarized in Table 4-3. Standard Deviation for foundation heights was set equal to 0.5 feet. 16
Economics Appendix – Draft Report - Orestimba Creek Feasibility Study, Stanislaus County, California – September 2012 Table 4-1: Standard Deviations for Risk and Uncertainty in Structure & Content Value UNCERTAINTY IN VALUE (INPUT TO HEC-FDA) USE CATEGORY Structure- Coefficient of Variation (%) Content- Coefficient of Variation (%) Residential (SFR & MFR) 12 12 Mobile Homes 14 14 Office 2-Story 13 14 Office 1-Story 13 16 Retail 12 14 Retail-Furniture 12 20 Auto Dealerships 12 12 Hotel 12 3 Food Stores 11 27 Restaurants 12 3 Restaurants-Fast Food 12 13 Medical 11 46 Shopping Centers 11 23 Large Grocery Stores 12 4 Service (Auto) 12 4 Warehouse 14 31 Light Ind. 12 19 Heavy Ind. 12 31 Government 12 16 Schools 14 33 Religious 13 40 Recreation 12 13 Automobiles 15 N/A Table 4-2: Standard Deviations for Depth-Damage Percentages - Residential Damage Category Structural (S) / Content (C) Depth in Feet -1 0 1 2 3 4 5 6 7 8 9 10 % Damage to Structure/Content SFR1 S 3 13 23 32 40 47 53 59 63 67 71 73 Std. Dev. 3 2 2 2 2 2 2 2 2 2 2 3 C 2 8 13 18 22 26 29 32 34 36 37 38 Std. Dev. 2 2 1 1 1 2 2 2 2 2 2 2 SFR2 S 3 9 15 21 26 31 36 41 45 49 52 56 Std. Dev. 4 3 3 3 3 3 3 4 4 4 4 4 C 1 5 9 12 16 19 21 24 26 28 30 32 Std. Dev. 4 3 3 3 3 3 3 3 3 3 4 4 MFR1 S 3 13 23 32 40 47 53 59 63 67 71 73 Std. Dev. 3 2 2 2 2 2 2 2 2 2 2 3 C 2 8 13 18 22 26 29 32 34 36 37 38 Std. Dev. 2 2 1 1 1 2 2 2 2 2 2 2 MFR2 S 3 9 15 21 26 31 36 41 45 49 52 56 Std. Dev. 4 3 3 3 3 3 3 4 4 4 4 4 C 1 5 9 12 16 19 21 24 26 28 30 32 Std. Dev. 4 3 3 3 3 3 3 3 3 3 4 4 17
Page 1 and 2: Economics Appendix - Draft Report -
Page 39: Economics Appendix - Draft Report -
Page 91 and 92:
Economics Appendix - Draft Report -
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123 and 124:
Page 125 and 126:
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133:
show all

Orestimba Creek Feasibility Study - Stanislaus County

Create successful ePaper yourself

Delete template?

Save as template?