Rapid Cost Estimation for Storm Recovery Using Geographic Information System
by Rolando A. Berríos-Montero
B.S. in Industrial and Systems Engineering, June 1998, The Ohio State University M.S. in Engineering Management, June 2001, Polytechnic University of Puerto Rico B.S. in Civil Engineering, June 2012, Polytechnic University of Puerto Rico M.S. in Economics, June 2014, University of Puerto Rico
A Dissertation submitted to
The Faculty of The School of Engineering and Applied Science of The George Washington University in partial satisfaction of the requirements for the degree of Doctor of Philosophy
May 15th , 2016
Dissertation directed by
Jason Dever Professional Lecturer of Engineering Management and Systems Engineering
and
Steven M. F. Stuban Professional Lecturer of Engineering Management and Systems Engineering
The School of Engineering and Applied Science of The George Washington
University certifies that Rolando A. Berríos-Montero has passed the Final
Examination for the degree of Doctor of Philosophy as of March 18 th , 2016. This is the final and approved form of the dissertation.
Rapid Cost Estimation for Storm Recovery Using Geographic Information System
Rolando A. Berríos-Montero
Dissertation Research Committee:
Shahram Sarkani, Professor of Engineering Management and Systems Engineering, Dissertation Co-Director
Thomas Mazzuchi, Professor of Engineering Management and Systems Engineering & Decision Sciences, Dissertation Co-Director
Steven M. F. Stuban, Professorial Lecturer in Engineering Management and System Engineering, Committee Member
Pavel Fomin, Professorial Lecturer in Engineering Management and Systems Engineering, Committee Member
E. Lile Murphree, Professor Emeritus of Engineering Management and Systems Engineering, Committee Member
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©Copyright 2016 by Rolando A. Berríos-Montero All rights reserved
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Dedication
To my beloved wife Ana Ligia and my daughter Ana Cristina…
“…, there are three things we all should do every day. We should do this every day of our lives. Number one is laugh. You should laugh every day. Number two is think.
You should spend some time in thought. And number three is, you should have your emotions moved to tears, could be happiness or joy. But think about it. If you laugh, you think, and you cry, that's a full day. That's a heck of a day. You do that seven days a week, you're going to have something special.”
James Thomas Anthony "Jim" Valvano (March 4 th , 1993)
…because this is how the three of us live every day.
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Acknowledgments
I am deeply appreciative of my mother, father and my sister for their continued interest and support of my doctoral journey.
I would like to express my gratitude to my advisors Dr. Stuban and Dr.
Dever for their positive guidance and patience. Their direction and feedback really gave me insight and motivation to continue on this journey.
I am grateful to my classmates who constantly checked on my progress over the last two years. A special thanks to George Wilamowski and Thembani Togwe for caring and for all the influential discussions and support toward the dissertation path. Their support made the world of difference.
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Abstract
Rapid Cost Estimation for Storm Recovery Using Geographic Information System
The present research introduces a new approach to estimate the recovery costs of public property in the aftermath of a storm, by integrating Geographic Information
Systems (GIS). Estimating recovery costs for a disaster is a current concern for emergency responders. This work focuses on applying economic indicators, population data, and storm event tracking to GIS for rapidly estimating recovery costs. Firstly, recovery costs of historical events are normalized and adjusted for inflation, wealth, and population. Geospatial analysis is used to predict, manage, and learn political boundaries and population density. Secondly, rapid recovery cost estimation is accomplished by defining population, personal income, and gross domestic product. Finally, a jurisdiction fiscal capacity (JFC) is calculated illustrating the economic capability of jurisdictions to finance public property recovery, based on their economy size. The variability of estimated absolute errors between cost estimates and actual normalized costs are also examined. The results reveal that JFC is a more suitable metric for rapidly estimating recovery costs of public properties than the method presently followed by the Federal Emergency
Management Agency. This new approach effectively aids the local government in providing quick cost guidance to recovery responders, while offering the ability to construct accurate recovery cost estimates.
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Table of Contents
Dedication ...... iii
Acknowledgments...... v
Abstract ...... vi
Table of Contents ...... vii
List of Figures ...... ix
List of Tables ...... xi
List of Acronyms ...... xii
Chapter 1. Introduction ...... 1 1.1 Systems Engineering Cost Estimation ...... 1 1.2 Problem Statement ...... 2 1.3 Purpose ...... 3 1.4 Approach ...... 4 1.5 Significance ...... 7 1.6 Limitation ...... 7 1.7 Outline ...... 8
Chapter 2. Literature Review ...... 10 2.1 Actual cost estimation models ...... 10 2.1.1 Components of actual cost estimating models ...... 12 2.1.2 Florida public hurricane loss projection model ...... 16 2.2 Cost estimation...... 19 2.3 GIS-based cost estimate ...... 22
Chapter 3. Data ...... 29 3.1 Storms ...... 30 3.2 Historical recovery cost ...... 32 3.3 Population and economic indicators ...... 32
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Chapter 4. Methodology ...... 35 4.1 Methodology approach ...... 35 4.2 Storm analysis ...... 38 4.3 Normalized Cost ...... 42 4.4 Jurisdiction fiscal capacity ...... 43 4.5 Recovery cost estimation ...... 44
Chapter 5. Results and Analysis ...... 48 5.1 Mahalanobis Distance (MD) ...... 52 5.2 Hurricane Georges as outlier ...... 56 5.3 Median absolute deviation (MAD) ...... 58 5.4 GIS output ...... 71 5.5 Cost exceedance probability ...... 82 5.5.1 Random sampling methodology ...... 83 5.6 Log-normal distribution ...... 86
Chapter 6. Conclusion ...... 89 6.1 Recommendations for future research ...... 91
References ...... 92
Appendix A: Jurisdictions affected per storm ...... 103
Appendix B: Mahalanobis Distance MATLAB ® code ...... 133
Appendix C: Cost exceedance probability MATLAB ® code...... 135
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List of Figures
Figure 4.1 GIS Model Flow Diagram ...... 36
Figure 4.2 ArcMap® Attribute table implemented for hurricane Irene ...... 38
Figure 4.3 Count per month of storms ...... 39
Figure 4.4 Cumulative distribution function of storms ...... 39
Figure 4.5 Puerto Rico’s storm count ...... 41
Figure 4.6 ArcMap ® Fields Calculator window for recovery cost estimation ...... 44
Figure 5.1 7Bar graph of the normalized recovery cost and the recovery cost estimate. .. 51
Figure 5.2 8Mahalinobis distance plot ...... 55
Figure 5.3 9Euclidian distance plot ...... 55
Figure 5.4 10 Mahalinobis distance scatterplot ...... 57
Figure 5.5 11 Actual FEMA estimates and the Rapid Cost Estimates Error Bound Plot..... 65
Figure 5.6 12 Adjusted FEMA estimates and the Rapid Cost Estimates Error Bound Plot . 65
Figure 5.7 13 Error absolute values deviation from median: Rapid Cost Estimate ...... 66
Figure 5.8 14 Error absolute values deviation from median: Actual FEMA estimate ...... 67
Figure 5.9 15 Error absolute values deviation from median: Adjusted FEMA estimate ..... 67
Figure 5.10 16 Normal probability plot: Rapid Cost Estimate ...... 69
Figure 5.11 17 Normal probability plot: Actual FEMA Estimate ...... 69
Figure 5.12 18 Normal probability plot: Adjusted FEMA Estimate ...... 70
Figure 5.13 19 NOAA-Historical Hurricane Tracks Hugo (1989) ...... 72
Figure 5.14 20 ArcMap® Hugo GIS-based model output ...... 73
Figure 5.15 21 NOAA-Historical Hurricane Tracks Hortense (1996) ...... 74
Figure 5.16 22 ArcMap® Hortense GIS-based model output ...... 75
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Figure 5.17 23 NOAA-Historical Hurricane Tracks Georges (1998) ...... 76
Figure 5.18 24 ArcMap® Georges GIS-based model output ...... 77
Figure 5.19 25 NOAA-Historical Hurricane Tracks Jeanne (2004) ...... 78
Figure 5.20 26 ArcMap® Jeanne GIS-based model output ...... 79
Figure 5.21 27 NOAA: Historical Hurricane Tracks Irene (2011) ...... 80
Figure 5.22 28 ArcMap® Irene GIS-based model output ...... 81
Figure 5.23 29 Cost exceedance probability curve ...... 85
Figure 5.24 30 Log-normal distribution ...... 87
Figure 5.25 31 Kolmogorov-Smirnov Test MATLAB® output ...... 88
Figure 6.1 32 Puerto Rico storm recovery cost trends...... 90
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List of Tables
Table 3.1 GIS database by layer...... 29
Table 3.2 Storm and hurricane events ...... 31
Table 3.3 Economic indicators ...... 33
Table 4.1Population...... 46
Table 5.1 Comparison between actual costs normalized to year 2012, FEMA estimate, and the rapid costs estimates...... 50
Table 5.2 Percentage and error difference between normalized cost and the rapid cost estimation as an input to analyze MAD...... 59
Table 5.3 Percentage and error difference between normalized cost and the FEMA estimation as an input to analyze MAD...... 60
Table 5.4 Rapid Cost Estimate sorted data per percentile and the MAD...... 61
Table 5.5 FEMA Estimation sorted data per percentile and the MAD output per storm. 62
Table 5.6 6Comparison between new adjusted FEMA estimate MAD and Rapid Cost Estimate MAD ...... 63
Table 5.7 Regression Analysis R 2's ...... 70
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List of Acronyms
CDF Cumulative Distribution Functions
C.F.R. Code of Federal Regulations
ECDF Empirical Cumulative Distribution Functions
DLI Damage Loss Indicator
FEMA Federal Emergency Management Agency
GAO U.S. Government Accountability Office
GDP Gross Domestic Product
GIS Geographic Information Systems
H Hurricane
JFC Jurisdiction Fiscal Capacity kn knots
MAD Median Absolute Deviation mb millibars
MD Mahalinobis Distance
N North
NOAA National Oceanic and Atmospheric Administration
PDA Preliminary Damage Assessment
PI Personal Income
PREMA Puerto Rico Emergency Management Agency
R2 R-Square
SS Severe Storm
TS Tropical Storm
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TTR Total Taxable Resources
USD U.S. Dollar
W West
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Chapter 1. Introduction
1.1 Systems Engineering Cost Estimation
Systems engineering is a disciplined approach to design, plan, specify, integrate, implement, operate, and maintain complex systems. Any system development relies on a planning process, however one significant task that makes the planning process difficult is cost estimation. Cost estimation provides necessary information to facilitate a decision making process regarding resources, equipment, materials, and supplies needed. Cost estimation information can even have a direct impact on a schedule or vice versa. More importantly, cost estimation is the fundamental process that allows the development of systems.
Certainly, decisions made while restoring public properties after a storm disaster drive emergency management systems’ recovery and operation costs. In order to receive adequate recovery funding, it is imperative to know and understand how to accurately estimate potential expenses to restore public properties. A well-developed cost estimation approach is a decision-support tool within systems engineering.
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1.2 Problem Statement
A system to rapidly estimate the cost of restoring public properties after a storm disaster would assist state and local governments by providing an indicator of resilience. A recovery cost estimation includes the cost of restoring public properties to their original condition, prior to the physical damage caused by the storm (Fujimi & Tatano, 2012). Such estimations tend to be onerous and time- consuming tasks for emergency management officials, because the costs of a natural disaster are linked to several factors and vary according to storm categories. Zandbergen (2009) states that the storm surge presents the greatest hazard to low-lying coastal areas, but the wind and rain hazards can have a greater impact because they can reach further inland. Therefore, these natural events often cause damage extending hundreds of miles inland, destroying public buildings, roads, and bridges.
Estimating the reconstruction costs in the aftermath of a storm requires a careful and time-consuming analysis (Dorra, Stafford, & Elghazouli, 2013; Fujimi
& Tatano, 2012; Coffman & Noy, 2011; Huang et al., 2008; Tatano & Tsuchiya,
2008; Dutta, Herath, & Musiake, 2003). This research concentrates on rapid recovery cost estimation using a Geographic Information Systems (GIS), and includes costs related to public property assets such as public buildings, roads, bridges, water systems, and the power transmission infrastructure. The recovery cost estimate assumes that public properties physically affected by a storm are to be restored to their original condition.
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1.3 Purpose
This research considers the cost estimation approach of the U.S. Federal
Emergency Management Agency (FEMA), which is based on a preliminary damage assessment (PDA). Then, a proposed method is demonstrated to estimate this cost by applying jurisdiction economic indicators, population, and storm tracks to a GIS.
Currently, each jurisdiction affected by a storm event sends local private contractors, government representatives, and FEMA officials to visually inspect damage sites and provide early cost estimates under disaster conditions. These cost estimates are considered by FEMA when completing a PDA, which is a joint assessment to determine the impact of the storm damage and to decide whether federal assistance is needed. The PDA considers statewide and countywide per- capita indicators, which are adjusted annually for inflation. The statewide and countywide indicators for the United States in 2012 were 1.35USD and 3.39USD, respectively (GAO, 2012). These indicators are determined by FEMA based on
1983 per capita personal income nationwide. Moreover, the actual recovery costs are recorded and maintained by FEMA, because this information is a necessary part of its Public Assistance Grant Program. This program assists all U.S. jurisdictions in responding to and recovering from major disasters or emergencies declared by the President (GAO, 2012).
The purpose of this research is to identify and propose a more accurate method to estimate recovery costs of physically damaged public properties. The
3 integration of GIS-readable database, including jurisdiction economic indicators, public building locations, political boundaries, municipality population, and storm track is a more suitable approach than FEMA-used statewide per capita indicator for rapidly estimating recovery costs of public properties in the aftermath of a storm event.
1.4 Approach
This investigation presents a systematic approach to rapidly estimating the recovery costs for public properties by incorporating the jurisdiction fiscal capacity (JFC), population, and event track data in a GIS. The GIS-readable database includes public jurisdiction economic indicators, building locations, political boundaries, municipality populations, and storm intensity profiles. Using the database, the systematic cost estimate model simulates storm damages based on historical storm data and normalized damage costs. Then, the JFC is determined in U.S. dollars by calculating the total taxable resources (TTR). This provides a more sensitive adjustment for growth over time in a jurisdiction than does an adjustment for inflation based on personal income (GAO, 2001). A more suitable public property cost estimation can be obtained from the JFC because it reflects a jurisdiction’s current fiscal reality, as well as its response and recovery capabilities (GAO, 2012). TTR is a comprehensive measure of all sources of income that a state could conceivably tax, irrespective of the state’s actual tax policies (Compson, 2003). Therefore, integrating the JFC into the model enables us to estimate recovery costs and improves our ability to assess a jurisdiction’s capacity to respond and recover on its own.
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This research presents a new approach to estimating the costs of restoring public properties that have suffered physical damage. It is shown that integrating a
GIS-readable database is a more suitable approach to rapidly estimating recovery costs than is the statewide per capita indicator used by FEMA. Moreover, this results from the proposed model better reflecting actual recovery costs than does the current FEMA method.
A GIS-based cost estimation model requires parameters that describe the subject geography in the geodatabase. Similarly, the GIS-based application provides resources to display storm event tracks. These data are then overlaid with maps of the population, industrial public properties, and estimated costs in order to provide a rapid recovery cost estimate. GIS layers such as storm tracks, political boundaries, industrial public properties, population, and historical recovery costs have been developed into a geodatabase to rapidly and more accurately estimate costs in the aftermath of a storm event. For instance, Elsner (2003) and Camargo et al. (2007) used GIS layers in cluster methods on storm locations to construct storm tracks.
First, the GIS software is used to obtain shapefiles that describe the basemap of the study area. These shapefiles include political boundaries, storm tracks, jurisdictions affected by storms, and public buildings. Second, attribute tables are loaded with economic indicators, recovery costs, and population data.
Population and economic indicators are essential to adjusting recovery costs over time to a notional economic value in year 2012. The cost estimations are normalized to adjust for inflation, wealth, and population. Then, the JFC
5 measurement is calculated to rapidly and more accurately estimate the recovery costs. Recovery cost estimations are important for the accountability of emergency responder officials. These officials develop a general framework that implements appropriate analytical models to estimate the recovery costs (FEMA, 2011). This research also includes an exceedance probability analysis to estimate yearly recovery costs that exceed specified amounts. Using a GIS provides several benefits to emergency responders, including quick access to prior recovery cost data, data analyses, and the presentation of results (Burrough, 2001). This systematic GIS-based cost estimation approach interacts with a geodatabase of economic indicators and storms in order to rapidly estimate the costs of recovery for public properties. Moreover, an exceedance probability analysis determines the likelihood of a recovery cost occurring. Then, the JFC analysis provides new insights into how jurisdictions have responded to needs and services, while still being able to analyze variations across states (Mikesell, 2007).
The cost exceedance probability is calculated by fitting the normalized cost data set to an exponential distribution, and then calculating the storm event values from a cumulative distribution function. Because the frequency of a storm event is unknown, this event is defined as a random variable x, with an exponential distribution. In other words, an exponential distribution is used to estimate the relevant costs when a storm occurs. Hence, considering an exponential and a
Poisson distribution, with specified parameters, random variables for each storm can be generated in order to estimate the recovery costs based on a simulation with a large set of events. This process is repeated in a simulation at least 20,000 times
6 in order to obtain a cost exceedance probability curve and its 95% confidence band. An exponential fit uses the mean value to create an exponential distribution, from which the cost estimates may be sampled. The simulation is used to develop the cost exceedance probability curve. This curve shows the probability of any given recovery cost being exceeded after a storm, within a given cost range.
1.5 Significance
The significance of this work relies on the accuracy of cost estimations, within the time limitation constraint on emergency responders. Recovery cost estimation is important for the accountability of emergency responder officials, who develop a general framework implementing analytical models appropriate to estimating these costs. Using a GIS provides several benefits to emergency responders, including rapid access to prior recovery costs, data analyses, and the presentation of results (Burrough, 2001). Moreover, the JFC analysis provides insights into how jurisdictions have responded to needs and services, while still being able to analyze variations across states (Mikesell, 2007). This systematic
GIS-based cost estimation approach interacts with a geodatabase of economic indicators and storms to rapidly estimate the costs associated with the recovery of public properties.
1.6 Limitation
Emergency response agencies currently use a variety of approaches to assess the overall damage, loss, and recovery costs after a storm event (Nadi et al.,
2010). This research is limited to accurate recovery cost estimations for public
7 properties, and presents a finite approach to rapidly estimating these costs by applying GIS technology. A geospatial approach is applied to identify municipality boundaries and population densities, as part of the cost estimation calculation. Storm intensity characteristics, such as precipitation and sustained winds, are beyond the scope of this research. The investigation focuses on the jurisdiction of Puerto Rico to validate the GIS-based cost estimate model, and considers only those storm events that damaged public properties.
1.7 Outline
The dissertation is organized as follows:
Chapter 2 presents the literature review. This is an exhaustive exposition of previous research on cost estimation, as well as recovery based on GIS-based cost estimations. Examples of previous recovery cost applications are presented. In addition, this chapter explores the links between previous solutions and the proposed GIS-based cost estimate approach in order to rapidly estimate the recovery costs for public properties.
Chapter 3 presents the data and data sources used during the research.
Types of data and domains are analyzed to demonstrate the capability of the formulation to estimate recovery costs. Some data are overlaid with population maps, public building properties, economic indicators, and estimated costs to rapidly provide cost information for the identified storm events.
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Chapter 4 discusses the rapid recovery cost estimation method, including using a GIS. Then, the chapter discusses applying a statistical analysis to evaluate the storm occurrence distribution. Moreover, it presents using the quantitative formulation to determine a recovery cost estimate in a timely manner using a
ArcMap ®, a GIS software.
Chapter 5 presents and analyzes the results of the GIS-based cost estimation model. The results and GIS outcomes are presented for various storms, and the major finding are discussed. The outcomes show that incorporating a fiscal capacity indicator in the GIS-based cost estimation analysis produces estimated costs that are close to the actual costs.
Chapter 6 concludes the dissertation with a discussion of the GIS-based cost estimation, applying the JFC, and provides recommendations for possible future work.
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Chapter 2. Literature Review
This chapter presents an exhaustive exposition of current cost estimation models, previous research on cost estimation, and applying GIS to recovery cost management. This includes introducing concepts such as loss and recovery costs.
Moreover, the GIS-based model for rapid recovery cost estimation is introduced because this is the focus of the research described here.
2.1 Actual cost estimation models
Cost estimation techniques are widely employed to estimate the financial value of the probable damage to properties caused by storms. These techniques help government emergency responders and insurance companies to identify how much damage has occurred and estimate how much claimants will apply to recover for losses.
Watson and Johnson (2004) describe the actual components of prediction models. However, these are highly abstracted because the models are proprietary and mostly used by insurance companies and mortgage holders, which limits government agencies and insurance companies in conducting exhaustive benchmark analyses on the effectiveness of the models. Nevertheless, these models include a number of common components. This section describes a few cost estimation models by applying them to real scenarios.
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Storm models have always attracted a lot of attention among practitioners and academic researchers. Storms models are quite different to traditional actuarial models or methods used to determine rates based on previous recovery costs for a given set (Watson & Johnson, 2004). In terms of modeling low probability and high severity events such as windstorms, Watson and Johnson (2004) have also noted that actuarial methods lose credibility. Theoretically, cost estimation models based on current storm exposures should be able to produce more accurate results.
However, it is difficult for emergency responders or others involved in the process to assess the validity of these models. For instance, insurers find it challenging using these models to establish fair and accurate rates (Watson & Johnson, 2004).
A wide variety of research is available on the differences among storm models, including studies by engineers, insurance researchers, and meteorological researchers. These researchers have been able to establish differences based on meteorological assumptions, such as topography, decay rates, wind fields, and landfall frequencies. A few other factors have also been identified as important, including changes in global climate, surges in demand, insurance contracts, and expenses based on loss adjustments (Canabarro, 2000). For instance, the Florida
Commission on Hurricane Loss Projection Methodology (2007), in a report to the
Florida House of Representatives, examined the variations in model outputs across all models, using county level as the benchmark. They found that two models, namely the Public Model and ARA Model, had the most observations outside the set benchmark. A few other researchers have found differences in the ultimate loss cost models, based on the assumptions in the models. For example, the range of
11 loss costs can be quite large, with a 3 to 1 ratio, or higher (Watson et al., 2004).
This ratio could be even higher for inland areas. These variations in loss costs cause disparities in pricing models for some locations.
For instance, insurance companies have developed catastrophe models, which use complex computer simulations. Insurers worldwide use these models to predict potential recovery costs after hurricanes, tornadoes, or earthquakes. They use the simulations to help manage portfolios and make decisions on risk and pricing. Currently, four private companies offer storm recovery cost estimation models that have been approved for use in Florida: AIR Worldwide, Applied
Research Associates, EQECAT, and Risk Management Solutions (Jeanine-Brown,
2011).
The implications of these models are wide. Variations among the models affect the recovery costs, pricing, and premiums and, ultimately, on insurance- linked securities. There is an increasing need for in-depth research in this area in order to develop better models and, thus, better estimates with less variation
(Jeanine-Brown, 2011).
2.1.1 Components of actual cost estimating models
Storm cost estimation models usually consist of five critical components (Watson
& Johnson, 2004):
1. Input databases
2. Wind models
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3. Boundary layer models
4. Damage function
5. Frequency of occurrence models
A description of each component follows.
Input databases: Existing cost estimation models use an input database with a minimum of three input data sets (Watson & Johnson, 2004):
a) Land cover data sets include information on the general coverage of
the area within the scope of exposure. This may vary in the level of
detail, from basic information (e.g., is it land or sea) to more
sophisticated categorizations, such as the trajectory-based model with
72 land type classifications.
b) Exposure data sets contain data that describe the location and the
value of the risk. These data sets also contain information on the
types of structures within the scope of exposure, as well as the
effectiveness of code enforcement, which significantly influences the
extent of damage during impact. Because the complete range of
construction types in an area may be unknown, data sets are based on
the typical construction mix in the area.
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c) Historical storm tracks and intensities are usually maintained in the
library for simulations of historical events and analyses of their
frequency.
Wind models: Like the land models, wind models range in complexity, from the simple Rankine Vortex model to complex parametric models to full three- dimensional physics models. Almost all wind models used by insurance companies are parametric (Malmquist & Michaels, 2000). These models employ simple storm parameters such as forward speed, minimum central pressure, radius of maximum winds, and so forth.
Boundary layer models: These models correct the results produced by the wind models when the raw winds hit the surface conditions. In theory, this model adjusts the results using a multiplication factor. However, there is no consensus in the literature on what the correct factor should be. It is generally about 0.85 over water, and 0.7 over land, but varies greatly in complexity for various terrain types.
Damage function: The damage function associates the wind deposited on an exposure site to the damage expected at the site. Damage functions may generally be grouped into three broad classes (Malmquist & Michaels, 2000):
a) Claims based
b) Engineering judgment
c) Theoretically based
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Claims-based functions analyze actual claims submitted to insurance companies. Despite their logical simplicity, such estimates are largely subjective, and depend on several administrative, political, and other considerations that differ between storms (Watson & Johnson, 2004).
Engineering judgment-based functions are based on the damage to structures, as determined by an engineering survey. Here too, individual interpretation may vary substantially (Chen et al., 2009).
Theoretical functions are based on the physics of the behavior of structures.
Although human judgment in this model is minimal, this model must be compatible with the other components of the overall loss estimation model
(Dunion et al., 2003).
Frequency of occurrence: The components mentioned so far are used to estimate the magnitude of the loss for a single occurrence of an event. In order to estimate holistic levels of losses from hurricanes in a particular area, the frequency component is used. There are three common approaches to including frequency information:
a) Rely on historical events
b) Fit and smooth probabilities along coastal segments
c) Reproduce hurricane formation and movement in a realistic fashion
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Relying on historical events presumes that future tropical cyclone activity will follow patterns similar to those that have occurred previously. The second approach involves fitting the frequencies of historical events by coastal segments in order to match modeled landfalls (Schwerdt, Ho, & Watkins 1979). The third approach can be accomplished using either statistical or climate models. The statistical methods can be summarized as follows (Watson & Johnson, 2004):
a) Historic storm set estimation
b) Monte Carlo simulation and estimation
c) Maximum likelihood estimation approach
2.1.2 Florida public hurricane loss projection model
In this section, the discussion moves away from the theory to examine models being used in practice. As an example, the Florida loss prediction model is considered. In terms of design, the model is composed of three components (FIU Public Hurricane Loss
Projection Model, 2014, cited by Johnson & Watson, 2004):
a) Wind vulnerability (engineering)
b) Insured loss cost (actuarial)
c) Hazard (meteorology)
This computer platform has further sub-components, and is designed to accommodate additional hook-ups, if required (FIU Public Hurricane Loss Projection
Model, 2014). Apart from assessing hurricane risks, the model can predict expected 16 annual losses for insured residential areas in Florida, up to the zip code level. The complete model for risk assessment has been built from several parts, including: the wind field model, the vulnerability model, the exposure study, actuarial components, and the computer platform. Most models use a regression analysis of claims data to define the vulnerability of homes. Instead, this model defines damage using a different component approach that considers the resistance capacity of each component of a home and the wind forces produced at increasing increments of wind speed (Pinelli et al., 2004).
The estimated loss can be broken down into components of structure, content, and additional living expenses. Further portfolio classifications by construction type and territory ratings, and combinations thereof, are also possible in this model. For a given portfolio of policies, the model can generate the probability of exceedance, return time, and probable maximum loss (Pita et al., 2013).
Components of the wind models include the following (FIU Public Hurricane Loss
Projection Model, 2014):
a) Storm track and intensity model: Generates storm tracks and intensity for
simulated hurricanes based on historical initial states
b) Inland storm decay model: Calculates decay after landfall
c) Wind field model: Creates open terrain wind speeds for hurricane-affected
zip codes
d) Gust factor model: Generates peak wind speeds
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e) Terrain roughness model: Corrects wind speed for terrain roughness
f) Wind probabilities model: Creates wind probabilities
Components of the vulnerability model include the following (FIU Public
Hurricane Loss Projection Model, 2014):
a) Engineering simulation model: Simulates possible wind damage to the
structure, interior, and content
b) Engineering damage model: Produces damage matrices and ratios for a
structure
c) Engineering mitigation model: Creates vulnerability functions (damage
matrices) for mitigated structures
Components of the insured loss model include the following (FIU Public
Hurricane Loss Projection Model, 2014):
a) Policy modifications model: Models deductibles and policy limits
b) Insured loss actuarial model (probabilistic): Estimates annual loss costs for
each policy, or portfolio of policies, or by area and construction type,
including adjustments for deductibles and limits
c) Insured loss actuarial model (scenario based): Creates expected loss costs for
a specific hurricane affecting a given area.
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The reliability of a model has significant implications for several institutions, and their major decisions. However, in their current state, these models do not show consistently accurate results (Watson & Johnson, 2004). Although the primary improvement scope lies in the field of meteorology, substantial steps in related fields, such as computational statistics, and disclosure efforts will help to make the science of recovery cost estimation more reliable.
2.2 Cost estimation
Cost estimations for public property damage occur shortly after a natural disaster. Certainly, states and local governments need cost information to make budgetary and feasibility decisions in order to complete a recovery system plan.
Estimating costs tends to be an onerous and time-consuming task for emergency management officials, because the cost of a natural disaster depends on several factors and varies according to the type of disaster. In addition, a GIS is a valuable tool in a natural disaster recovery cost estimation system because it can provide summarized information on demand.
AACE International, formerly known as the American Association of Cost
Engineering, defines cost estimating as “the predictive process used to quantify, cost, and price the resources required by the scope of an investment option, activity, or project.” From the literature, some studies use this process when determining economic loss or economic cost. Even though economic cost considers tangible and intangible damage (Dorra et al., 2013; Fujimi & Tatano,
2012; Coffman & Noy, 2011; Huang et al., 2008; Tatano & Tsuchiya, 2008; Dutta
19 el at., 2003), this investigation concentrates on cost estimation for tangible public properties. Tangible property includes physical public property assets such as public buildings, roads, bridges, water systems, and the power transmission infrastructure. On the other hand, intangible losses refer to the loss of human life, business interruption, ecosystem services, physical and psychological impacts, evacuation and rescue operations, health-care assistance, and traffic disruption, among others. The recovery costs for tangible properties include repair and replacement expenses to restore public properties to their original condition after suffering physical damage (Fujimi & Tatano, 2012).
However, the most appropriate measure of the economic cost is the market value of a property just before the disaster hit versus the replacement cost to rebuild it (Kousky, 2011). The replacement cost could be higher or lower, for several reasons. For instance, in a post-disaster scenario, some materials may be in short supply and more expensive substitutes might need to be used. In addition, labor may be in short supply, making wages higher, and driving the cost of rebuilding above what it would have been before the disaster (Olsen & Porter,
2008).
Cost estimation concepts have been tested previously. However, possible gaps in the accuracy of recovery cost estimations for infrastructure remain in the literature (Cheng & Yang, 2001; Tatano & Tsuchiya, 2008). In some cases, buildings and infrastructure may seem totally destroyed, but then turn out to be only partially damaged. One characteristic common to all natural disasters is that damage estimates calculated shortly after a disaster tend to be significantly
20 underestimated. In order to successfully complete a cost estimate, estimators need to understand clearly the project deliverables required to prepare estimates
(Dysert, 1997).
Cost estimation should depend on good systems of methods and procedures that meet the disaster recovery requirements (Hallegatte, 2014). For instance,
Franco et al. (2010) use a mathematical algorithm based on field surveys to obtain approximate cost estimates for repairs to components that tend to drive the overall repair cost. Algorithms provide specific steps to record the variables to be considered within the estimation methods and procedures.
Empirical studies and cost estimation methodologies have been completed.
For instance, the construction cost trend for the Louisiana Highway Department after Hurricane Katrina was studied by Cheng and Wilmot (2009). The authors showed how construction costs increased 51% in the aftermath of the storms, whereas the same construction costs decreased in other parts of the state. Even though they acknowledge that the trend in construction costs lasts for approximately two quarters, this economic competitive market behavior demonstrates a classic relationship between demand and supply. They conclude that the Louisiana Highway Cost Index trends show that Hurricanes Katrina and
Rita had a significant influence on Louisiana’s highway construction costs.
Similarly, Padgett et al. (2008) evaluated bridge damage patterns after Katrina, including damage attributed to wind, water inundation, and impact from debris, as well as examples of transportation system reconstruction and recovery measures to restore functionality. An analysis of their data indicated a relationship between the
21 surge elevation, damage state, and resulting repair costs. It was also shown that the normalized repair cost was typically highly nonlinear, as a function of damage state (Padgett et al., 2008). Karlaftis, Kepaptsoglou, and Lambropoulos (2007) developed an algorithm to support a three-stage approach for allocating repair funds to an urban bridge network following a natural disaster. Their methodology allocates available funds to repair bridges to their lowest acceptable operational level. Then, they estimate the bridge network repair costs.
To conclude, a rapid recovery cost estimation offers a better understanding of the impacts of a tropical storm disaster. In addition, it provides guidance for recovery management systems and the ability to construct an accurate cost estimation process, with built-in accountability for emergency responders. Here, a new recovery cost estimation model, including a GIS, is presented. This systematic GIS-based cost estimation approach interacts with a geodatabase of economic indicators and storms to rapidly estimate the cost of recovering and restoring public properties.
The link between cost estimation and the GIS application for rapid recovery cost estimation is discussed in more detail in the next section.
2.3 GIS-based cost estimate
In the previous section, we investigated the term cost estimation. In this section, we focus on using a GIS as a tool in cost estimation. Martin et al. (2001) estimated the road maintenance cost per kilometer by characterizing pavement maintenance costs using a GIS. The GIS-based model includes a road network
22 represented as connections of nodes and links. ArcView ® routing algorithms were developed to calculate the minimum distance path and minimum maintenance cost.
Similar applications have been adopted for emergency responders. When disaster strikes, a GIS helps responders assess emergency management and resilience activities. Reliable data on economic indicators and the recovery costs for public properties after storms, as well as how these costs differ spatially, would be valuable to disaster responders. A GIS is an excellent tool to maintain data and help provide rapid cost estimations, as well as to improve the communication and performance of management systems. GIS-based cost estimate applications also help to improve emergency response government agencies, hold government officials accountable, and promote responder effectiveness.
Integrating a GIS into the recovery cost estimation process provides a visual structure for conceptualizing different storm scenarios, and facilitating resiliency and recovery decision-making (Shrestha & Shrestha, 2014).
A GIS-based cost estimating system to support recovery cost estimations after a storm event is an excellent tool to facilitate decision-making at all levels of government. In fact, recovery cost estimation can be used to review and evaluate disaster recovery planning, construction codes, and future economic and land development.
During the past few decades, GISs have created opportunities for more detailed and rapid analyses of natural hazards. When weather-related disasters impact a jurisdiction, many states, counties, and cities use a GIS for emergency
23 response and disaster recovery. For instance, a GIS is used to create specialized maps, enabling emergency responders to make sense of the ruins left behind by a natural event (Nadi et al., 2010). A notable recent application was documented by
Armenakis and Nirupama (2013), where they include a GIS-based tool for disaster risks by integrating a spatial analysis with disaster management for the Toronto propane explosion in 2008. The study shows how including spatial overlays and attribute information related to people’s vulnerability helped to identify evacuation zones and critical infrastructure. Specifically, they cite Carr and Zwick
(2005), Church and Murray (2009), Kar and Hodgson (2008) with regard to geospatial information science and GIS technologies, which support site- suitability analyses in relation to the surrounding locations and population. Spatial analysis is a key technique when using a GIS as a tool for natural disaster recovery, because it locates various facilities in a given area, at the local and national level, depending on the area under consideration (Bansal, 2014).
Eveleigh, Mazzuchi, and Sarkani (2007) state that GIS technology is an excellent tool for managing data with a spatial component and exploiting spatial operators, such as contiguity, intersection, proximity, shape, and position, to support advanced data query, processing, and fusion. Furthermore, Yamamoto (2012) points out that a GIS has four major functions: (1) a database construction function; (2) an information analysis function; (3) an information sharing function; and, (4) a decision-making support function. These functions provide the information system with the link between the real world and the virtual world.
Moreover, he notes that GISs have such superior and unique functions that they
24 may become the basis for an information infrastructure that plays an important role in recovery and reconstruction.
Cost estimations for public properties can be extremely difficult to determine accurately in the aftermath of a storm disaster event. The cost assessment varies depending on the perceptions of the respondent and on site accessibility. Though a number of studies on recovery cost estimations have been completed over the years, there is insufficient research on applying a GIS to rapidly determine recovery costs. Cheng and Yang (2001) suggest a system that integrates a GIS-based cost estimation with construction-planning processes.
Similar GIS-based cost estimations can be achieved by integrating geographical systems into the information management of a population, storm tracks, and minimum pressure, in conjunction with economic cost damage indicators, in order to rapidly estimate recovery costs after a storm.
GIS capabilities allow an analysis of the relationship among the socioeconomics characteristics and physical features of a jurisdiction (Taupier &
Willis, 1994). For instance, FEMA uses Hazus as a GIS solution, which contains residents’ socioeconomic characteristics data, as well as structural industrial, commercial, and residential buildings (Schneider & Schauer, 2006). Hazus can model a hypothetical storm event and analyze the damage states of both residential and commercial properties. However, it is intensive in terms of data input, and takes a significant length of time to complete (Pan, 2014).
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The Hazus–MH Hurricane Wind Model enables users to estimate the economic and social losses from a storm, and facilitates a more accurate way of preparing for eventualities from all spheres. Relevant stakeholders, primarily state officers, often use the information provided by this model to evaluate, plan for, and mitigate the effects of hurricanes. The Hazus–MH Hurricane Wind Model makes this possible by employing a state-of-the-art wind field model, which has been calibrated and validated using full-scale hurricane data. This version of the
Hazus–MH model incorporates sea surface temperatures in the boundary layer analysis, and calculates wind speed as a function of translation speed, central pressure, and surface roughness (Hazus-Multi Hazard Hurricane Wind Model,
2014).
Currently, the recovery costs for public properties are estimated by the local government and FEMA by applying personal income per capita. An independent auditor’s report, GAO-12-838, from the U.S. Government
Accountability Office (GAO), states that FEMA relies on the personal income indicator to determine and estimate whether to recommend to the President that a jurisdiction needs public assistance funding after a natural disaster (p. 2). This indicator has been 3.50USD per capita since 2013. Geographic indicator differences affect the level of need in each jurisdiction (Compson, 2003). FEMA’s current PDA approach does not accurately reflect public property recovery costs or whether a jurisdiction can recover from a disaster without federal assistance
(GAO, 2012).
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A systematic approach that rapidly adjusts cost estimations would more accurately reflect the variations in costs (GAO, 2013). This can be achieved by integrating a geographical system into reliable data of a storm’s profile, recovery costs, political boundaries, population, and economic indicators, which include inflation, personal income, gross domestic product (GDP), and wealth. These data can be utilized as the key input to providing a storm event recovery solution. The fact that public infrastructure grows as an economy develops (Imran & Niazi,
2011) gives us a reason to consider a jurisdiction’s economic indicators in a GIS analysis. This links the analysis to GDP and population, which relates to public infrastructure literature. GDP is a measure of a jurisdiction's current production of goods and services in a certain period, and its fluctuations can be explained by changes in the population. In macroeconomics, GDP is the broadest economic indicator measuring a country's economy, and is often considered a lagging indicator (Kitchen & Monaco, 2003). In addition, GDP is considered the basic economic indicator of the wealth of a region. The literature on public infrastructure and growth focuses on how the demand for a physical infrastructure has direct and indirect effects on economic growth (Agénor & Moreno, 2006;
Hashimzade & Myles, 2010; Imran & Niazi, 2011). In fact, public property reconstruction increases GDP because there is an increase in construction spending in affected jurisdictions in the years following a natural disaster (Cashell &
Labonte, 1992).
The GIS-based cost estimate solution described here demonstrates how to rapidly estimate recovery costs for public properties. The results show clear
27 evidence that incorporating a fiscal capacity indicator into a GIS-based cost estimation analysis produces a recovery cost that is close to actual recorded costs.
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Chapter 3. Data
This research presents a GIS-based model to rapidly estimate the recovery costs for public properties after a storm event. As an application, we focus on the island of Puerto Rico, which is located in the Caribbean Sea and has an area of
3,425 square miles. The island is centered at 18.15° N, 66.30° W. This application requires parameters to describe the subject geography and the storm in the geodatabase. Similarly, the GIS application involves mapping rare and storm event tracks. Then, these data are overlaid with maps of the population, public building properties, and estimated costs in order to rapidly provide cost information on storm events. GIS layers such as storm tracks, political boundaries, public building properties, and population have been developed into a geodatabase to rapidly and accurately estimate costs in the aftermath of a storm event. The GIS layers are described in Table 3.1.
Table 3.1 GIS database by layer
Field GIS Layer Type Format Description and Data Sources Attribute Event track Line Vector Type Storm and hurricane tracks, data extracted from NOAA, FEMA, PREMA, and National Weather Service Forecast Office Political Polygon Vector Length Administrative areas extracted boundaries from topographic data Building properties Polygon Vector Type Public buildings shapefiles from Puerto Rico Industrial Development Company (PRIDCO) Population Polygon Vector Value Population data collected from US Bureau of Labor
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Estimated cost Polygon Vector Value Dollar value based on population and JFC
3.1 Storms
Historical data of storm profiles and tracks are extracted from the Historic
Hurricane Track database maintained by the National Oceanic and Atmospheric
Administration (NOAA) (NOAA/Office for Coastal Management, 2014). The
Hurricane Track database contains storm event names, dates, coordinates, storm categories, and storm profiles, such as minimum pressure in millibars (mb). The storm historical data for this work consider the following event classifications: severe storms (SS), tropical storms (TS), and hurricanes (H). These storms all occurred from 1950 to 2011 and within 65 nautical miles of Puerto Rico. The scale used to differentiate the severity of types of storms and hurricane is based on wind intensity. For instance, an (SS) is a natural event in which one-minute sustained surface winds are less than 33 knots (kn). Then, a (TS) has a maximum one-minute sustained surface wind speed ranging from 34 kn to 63 kn, (H1) has a one-minute sustained surface wind of at least 64 kn, (H2) has a one-minute sustained surface wind speed of at least 83 kn, (H3) has a one-minute sustained surface wind speed of at least 96 kn, (H4) has a one-minute sustained surface wind speed of at least
113 kn, and (H5) has a one-minute sustained surface wind speed of 137 kn, or more (NOAA/National Weather Service, 2014).
The attributes of storms considered in this study are those reported by
FEMA or the Puerto Rico Emergency Management Agency (PREMA) public records since 1950, and are shown in Table 3.2. Despite several storms striking
30 and making landfall in Puerto Rico before 1950, the lack of data and records on public property damage probably resulted in an undercount prior to 1950.
Table 3.2 Storm and hurricane events within 65 nautical miles of Puerto Rico. Historic Hurricane Track database maintained by the National Oceanic and Atmospheric Administration. *The closest storm location to Puerto Rico centroid.
Max. Min. Julian Name or Location* Wind Date Pressure Category Day FEMA ID N W Speed (mb) (kn) 8/23/1950 236 Baker 18 67 1007 35 TS ⁰ ⁰ 9/11/1955 254 Hilda 19.2 65.6 1002 40 TS ⁰ ⁰ 8/12/1956 225 Betsy 17.8 65.7 991 80 H1 ⁰ ⁰ 9/15/1975 258 Eloise 19.0 65.6 1007 30 TS ⁰ ⁰ 9/4/1979 247 Frederic 18.1 65.8 1003 45 TS ⁰ ⁰ 10/10/1985 283 DR-597 18.3 66.1 1019 25 SS ⁰ ⁰ 11/26/1987 330 DR-746 18.3 66.0 1009 40 SS ⁰ ⁰ 9/18/1989 261 Hugo 18.2 65.5 958 110 H2 ⁰ ⁰ 9/16/1995 259 Marilyn 18.5 65.2 952 95 H2 ⁰ ⁰ 9/10/1996 284 Hortense 18.0 66.9 989 70 H1 ⁰ ⁰ 9/21/1998 264 Georges 18.2 66.3 968 100 H2 ⁰ ⁰ 5/7/2001 127 DR-1372 18.2 66.2 1015 34 SS ⁰ ⁰ 11/8/2001 312 DR-1396 18.1 66.1 1016 31 SS ⁰ ⁰ 11/15/2003 319 DR-1501 18.2 66.0 1010 34 SS ⁰ ⁰ 9/15/2004 320 Jeanne 18.3 66.2 991 60 TS ⁰ ⁰ 10/9/2005 282 DR-1613 18.1 66.4 1007 35 SS ⁰ ⁰ 10/1/2008 274 DR-1798 18.3 66.0 1005 37 SS ⁰ ⁰ 5/27/2010 147 DR-1919 18.0 66.0 1015 28 SS ⁰ ⁰ 10/6/2010 279 Otto 18.7 66.1 1004 38 TS ⁰ ⁰ 5/20/2011 140 DR-4004 19.0 66.0 1014 23 SS ⁰ ⁰ 8/22/2011 234 Irene 18.3 66.2 990 65 H1 ⁰ ⁰
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3.2 Historical recovery cost
Historical storm event damage costs are also considered in the GIS database. Damage costs caused by a storm to public properties are recorded and maintained in FEMA public records, because it is a necessary information as part of its FEMA’s Public Assistance Grant Program. This program provides assistance to all U.S. jurisdictions in order to quickly respond to and recover from major disasters or emergencies declared by the President (GAO, 2012).
3.3 Population and economic indicators
Data related to population and economic indicators were acquired from the
US Bureau of Labor Statistics and the Puerto Rico Planning Board, respectively.
Economic indicators include inflation, real wealth per capita, GDP, and personal income, actual recovery cost is recorded and maintained by FEMA since such information is necessary to the Public Assistance Grant Program. This program is meant to provide assist all U.S. jurisdictions by assuring prompt response and recovery from presidential declared major disaster or emergencies (GAO, 2012).
Recovery costs before FEMA (1975) were obtained from PREMA regarding years with storm events. Table 3.3 summarizes the considered economic data for actual cost normalization. This recovery expense adjustment will be explained in detail in the methodology section.
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Table 3.3 Economic indicators applicable to the jurisdiction of Puerto Rico. Data sources include the U.S. Bureau of Labor Statistics and the Puerto Rico Planning Board. Recovery cost data sources include FEMA and PREMA Recovery Real Wealth Population Name or Inflation Year Cost per capita (thousand) FEMA ID (It) (Ct) (RWPC t) (Pt) 1950 Baker $2,543,747 -1.79 -2.35 2,206 1955 Hilda $5,739,836 -0.95 -3.23 2,232 1956 Betsy $5,889,482 1.23 2.43 2,250 1975 Eloise $9,374,393 8.56 0.18 2,914 1979 Frederic $2,398,533 6.46 0.21 3,141 1985 DR-597 $5,716,498 0.21 6.66 3,363 1987 DR-746 $8,528,283 2.08 0.67 3,420 1989 Hugo $40,609,290 2.82 0.50 3,479 1995 Marilyn $2,925,362 1.92 0.67 3,666 1996 Hortense $34,828,047 3.31 0.40 3,704 1998 Georges $117,911,767 0.05 25.36 3,770 2001 DR-1372 $5,147,725 0.58 1.92 3,815 2001 DR-1396 $4,853,317 0.58 1.92 3,815 2003 DR-1501 $6,996,153 1.38 0.83 3,825 2004 Jeanne $41,301,481 2.54 0.45 3,826 2005 DR-1613 $11,822,936 5.61 0.21 3,824 2008 DR-1798 $14,931,386 5.21 0.22 3,772 2010 DR-1919 $5,308,114 2.48 0.43 3,731 2010 Otto $16,337,825 2.48 0.43 3,731 2011 DR-4004 $7,397,528 1.09 0.96 3,714 2011 Irene $55,664,884 1.09 0.97 3,714
All data required to successfully apply the cost estimation model are administered, and calculations are made using the geospatial analysis software
ArcMap ®. ArcMap ® can manage and store data in attribute tables in order to facilitate the data entry process. Attribute tables are database components similar 33 to a spreadsheet, including a field calculator tool to create new data from historical data stored in a table. Integrating population, economic indicator, and historical cost data into a GIS-based cost estimation model provides new input data, such as normalized costs and the JFC, which can be used to rapidly estimate damage costs after a storm.
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Chapter 4. Methodology
The objective of this research is to provide a method of rapid cost estimation for recovery after a storm, using a GIS. The claim made in this investigation is as follows: applying a JFC is more suitable than applying statewide per capita indicators from FEMA when rapidly estimating recovery costs for public properties in the aftermath of a storm.
4.1 Methodology approach
GIS solutions employ geographic data sets such as contours, storm tracks, political boundaries, and population, among others. These data may be in the form of a shapefile, geodatabase, or spreadsheet. They also incorporate jurisdictions’ economic indicators to normalize historical recovery costs and to calculate the
JFC.
The GIS model in this research involves 5 stages as depicted in Figure 4.1:
(1) data collection and classification; (2) frequency of storms and analysis; (3) geodatabase development; (3) data processing to normalize cost and to calculate the JFC; (4) recovery cost estimation; and, (5) geographical representation information.
35
Start
Load data (Attribute Tables)
Personal County/City/ Population Municipality Income
Real Wealth Storm GDP per capita
Frequency of storms and analysis
Geodatabse
Shapefiles; Maps and storm tracks New Field
GIS visualization interface
Rapid recovery cost estimation
Geographical representation information
Figure 4.1 GIS Model Flow Diagram
36
First, an examination of the frequency of storms is performed. Second, the historical recovery costs reported by FEMA are normalized. The normalization calculation estimates the damage that would occur if storms from the past resulted in recovery costs for public properties in 2012. Third, the JFC is determined to show the economic capability of the jurisdiction of Puerto Rico to finance public property recovery based on the size of its economy. Then, the JFC is multiplied by the population size to rapidly estimate the recovery costs.
Cost estimation calculations are based on the data described in Chapter 3, which is stored using ArcMap ®. ArcMap® can manage and store data in attribute tables in order to facilitate the data entry process (Figure 4.2). Attribute tables are database components similar to a spreadsheet, including a field calculator tool to create new data from historical data already stored in a table. Integrating population, economic indicators, and public property recovery cost data into a
GIS-based cost estimation model provides new input data, such as normalized costs and the JFC, to rapidly estimate recovery costs for public properties after a storm. Finally, the cost exceedance probability is developed to provide guidance on recovery cost estimations.
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Figure 4.2 ArcMap® Attribute table implemented for hurricane Irene
4.2 Storm analysis
This work relies on data of storms that have occurred within 65 nautical miles of Puerto Rico and that have physically affected public properties. The data are acquired from NOAA: National Hurricane Center – Historical Hurricane
Tracks, FEMA: Disaster Declarations for Puerto Rico, and the Puerto Rico
Emergency Management Agency (PREMA): Disaster Historical Records.
Puerto Rico’s hurricane season runs from June 1 to November 30. Figure
4.3 shows the storm counts per month. Figure 4.4 illustrates the cumulative distribution functions (CDF) of these storms. The CDF graph shows that the probability value increases from zero to one (vertical axis), and the Julian days for
38 the assigned storms go from left to right on the horizontal axis. Figure 4.3 and
Figure 4.4 show that the peak storm activity period is September.
Figure 4.3 Count per month of storms that affected public properties in Puerto Rico. Data source: NOAA: National Hurricane Center – Historical Hurricane Tracks, FEMA: Disaster Declarations for Puerto Rico, and Puerto Rico Emergency Management Agency (PREMA). Figure similar to Malmstadt, Scheitlin, and Elsner (2009).
Storm Count since 1950 10 8 8
6 4 4 3 3 3 2 Count (since (since 1950) Count 0 0 0 May Jun Jul Aug Sep Oct Nov Month
Figure 4.4 Cumulative distribution function of storms from Figure 4.3. Figure similar to Malmstadt, J., Scheitlin, K., and Elsner, J. (2009).
1.00
0.80
0.60
0.40 Cumulative Cumulative Distribution 0.20
0.00 100 200 300 400 Julian Day
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A storm data distribution analysis is implemented to fit the data to the correct distribution. First, a storm frequency analysis is performed. The frequency of storms per year, which is a discrete distribution, is suspected to fit the Poisson distribution.
According to Chiasson (2013), a continuous random variable x is said to have an exponential λ distribution if it has the following cumulative density function (p. 238):
0, < 0 (4.1) = 1 − , ≥ 0 where x denotes independent events that occur at a constant average cost rate λ.
The Poisson distribution is suggested because storm events are independent, and the occurrence of an event increases or decreases the chance of another
(Malmstadt, Scheitlin & Elsner, 2009). The illustrated data set can be characterized well by a Poisson distribution, because its plot is skewed toward the end (i.e., the distribution is not symmetrical). See Figure 4.5.
The Poisson distribution is discrete. Given a certain storm event that occurs at a rate l , it models the probability that k of these events will occur within a specified period. The probability mass function is shown in equation (4.2):