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Climate Change & Extreme Weather Vulnerability Assessment Framework

2 Defining Objectives and Scope

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This section provides suggestions and resources for articulating objectives, selecting and characterizing relevant assets, and identifying climate variables for study. Together, these steps frame the scope of the vulnerability assessment and drive the details required for the analysis. They form bounds to the study, minimizing data collection and analysis activities that would ultimately be extraneous to study objectives.

While we recommend articulating the objectives of the assessment as a first step, agencies may find it useful to simultaneously work to characterize relevant assets and identify climate variables to study.

Formulating Study Teams

Deciding who will be involved in the study has a large impact on how the study is run and the final outcomes. The members of the study team will for the most part be dictated by the study objectives. Often, a cross-disciplinary team is needed to integrate long-range planning, engineering, and asset management considerations into the vulnerability assessment effectively. For instance, each of the following disciplines may have something to offer for the study:

  • Transportation planners are responsible for long-range planning of the transportation system, and regularly work with scenario planning and other tools for planning long-term investments and policies in the face of uncertain futures.
  • GIS specialists can provide invaluable expertise in both analyzing and displaying transportation assets and vulnerability information.
  • Asset managers may have valuable datasets and are familiar with the conditions of assets.
  • State climatologists can provide information and insight into historical climate data and trends, and in some cases future projections.
  • NOAA and University climate change research centers can provide projections targeted to your study area.
  • Maintenance personnel often have the best on-the-ground familiarity with the ways weather events affect transportation assets today, and what it takes to maintain the system in the face of these impacts.
  • Design engineers (e.g., structural, hydraulic, coastal, or other relevant disciplines) can provide input into the sensitivity of infrastructure to climate impacts and ideas/costs for adaptation solutions.
  • Natural resource agency personnel can provide insight into trends in the natural environment and understanding of how projected changes might impact ecosystem services.

2.1 Articulating Objectives

It is important to identify goals and objectives early in the vulnerability assessment process as they help determine the level of detail required in the analysis and the data and products that might be needed. When developing the objectives, consider the intended outcomes and target audiences. Objectives can be based on a range of activities or goals. Some questions to consider:

Example objectives include:

2.1.1. Examples from Practice: Articulating Objectives

Objectives deeply influence the scope and methodology of assessments. For example:

2.2 Selecting and Characterizing Relevant Assets

Transportation agencies need to decide which assets they wish to evaluate to meet the objectives of their assessment. Identifying the relevant assets for a vulnerability study and determining which characteristics of these assets to examine can help agencies narrow the scope of the vulnerability study. For example, if an agency would like to focus on a certain set of assets (e.g., owned or planned assets) it would begin the process by deciding which assets to include, assessing data availability for those assets, and understanding the timeframe and other important characteristics of managing those assets. When compiling this inventory, agencies should also gather any information that may help later to evaluate how resilient the asset is to climate stressors, and how costly damage to the asset or reductions in service could be. Example information types are provided below.

2.2.1 Asset Type

A wide range of asset types and system services could be considered in the assessment, depending on an agency's objectives. Transportation infrastructure such as roads, rails, and bridges will be a major focus for most agencies, but assets can also include support facilities, vehicles, and even ecosystem related assets for agencies interested in understanding how climate change will affect their environmental commitments or the ecosystem services on which the agency may rely. Some of the assets and systems that might be considered include:

2.2.2 Temporal Scope

The study goals and audience may drive the temporal scope of the assets being assessed for vulnerability. If the target audience includes maintenance staff, then the study might focus on seasonal effects to existing assets. Alternatively, if the goal of the assessment is to help a metropolitan planning organization consider climate change effects in their long-term planning efforts, then it may be useful to include the future, planned assets that are in the long-range transportation plan in the universe of assets reviewed for vulnerability. In general, if the audience for the study is concerned about assets with long design lives (and planned upgrades) or assets envisioned for the future, it is important to include these assets in the analysis. For instance, the goal of the study may be to provide input to capital and rehabilitation cycles, so that new assets and upgraded assets incorporate needed adaptations.

2.2.3 Asset Data availability

Data availability can be a limiting factor on the inclusion of assets in the study scope. A variety of data is needed for climate vulnerability assessments, only some of which may be easily gleaned from standard agency databases. In some cases, necessary data may be in multiple databases or in different formats

and may require significant effort to merge the information into a usable format. Typical data that might be needed for a vulnerability assessment includes:

2.2.4 Further Delineating Assets

In most cases, time and resource constraints prevent analyzing every asset in a transportation system. An important part of scoping the study, therefore, is finding a way to delineate which assets to examine. A number of different approaches have been used:

2.2.5 Examples from Practice: Selecting and Characterizing Relevant Assets

The pilot teams chose different ways of defining the scope of the assets to include. Many of these choices were related to the objectives of the overall analysis. In addition, these choices often reflected the jurisdictional boundaries of the agencies involved in the assessment or limits of the resources available. For example:

2.2.6 Resources for Selecting and Characterizing Relevant Assets

Assessing Criticality in Transportation Planning, FHWA 2011. This memo discusses approaches for narrowing the universe of transportation assets to study in a climate change vulnerability and risk assessment by assessing their "criticality" and otherwise narrowing study scope. It identifies common challenges, and draws on examples from the FHWA Adaptation Conceptual Model Pilots and the ongoing USDOT Gulf Coast Phase 2 study.

2.3 Assessing Asset Criticality

Performing a criticality assessment is one way to narrow assets for further study. It provides a structured way to identify the most important assets that an agency might wish to examine for vulnerability to climate change. Although useful, criticality assessments can be resource and data intensive. There are several approaches available for asset prioritization, falling into two broad categories (these general approaches can also be used to prioritize assets for reasons other than criticality):

Desk Review. One approach to formulating criticality criteria is to identify a broad range of criteria that capture use and access across a range of modes and systems. Assets are ranked based on data such as average daily traffic, functional classification, goods movement, emergency management, and expert judgment. Advantages of the approach include its transparency and replicability. However, lack of data on important elements of criticality, many of which are qualitative and locally specific, or not available from the private sector, could undermine results of the desk review in the eyes of the local stakeholders and decision makers. Moreover, the results are dependent on the weight applied to the various criteria; again, this weighting may not adequately capture local concerns.

Stakeholder Input. Determining asset criticality based on input from select stakeholders and local experts is a second approach to assessing criticality. With a stakeholder input approach, the project leaders will identify a group of stakeholders in the region with expert knowledge of specific interests (e.g., commercial activity, public safety, or road maintenance). The project leaders will then elicit feedback from these stakeholders on which assets are critical. Advantages of the stakeholder approach include getting buy-in from relevant stakeholders early in the process, encouraging collaboration and communication among stakeholders and actors likely to implement any adaptation strategies, accessing information that is not readily available in publicly-available datasets, and quickly assessing criticality without a lengthy research process. However, the results of the stakeholder -driven process are highly subjective, and the outcomes are dependent on the quality of the stakeholder engagement. For example, if project leaders decide to hold a workshop or series of workshops to solicit stakeholder feedback, the quality of the workshop facilitation, composition of workshop attendees, and level of participation from key experts will be important factors in the ultimate success of the stakeholder input approach.

Often, the two approaches are combined. Typically, a desk review will identify an initial list of critical assets based on commonly available data such as average daily traffic or economic information for the region (e.g., data on imports/exports from a particular port). The project team will then use the results of the desk review to inform and structure feedback from stakeholders and local experts.

2.3.1 Examples from Practice: Assessing Criticality

Figure 2: WSDOT Criticality Rating Scale - Description: This graphic displays a ciriticality rating scale used by Washington State DOT. Along the top of the scale are the numbers 1 through ten and the title: Criticality of Asset. Numbers 1 through 3.5 are labled "very low to low," and corresponding text notes that this typically involves non-NHS, low AADT, and alternative routes available. An accompanying photo shows a two-lane road. Numbers 3.5 through 6 are labled "moderate," and corresponding text notes that this typically involves: some NHS, non-NHS, low to medium AADT, serves as an alternate for other State routes. An accompanying photo shows an arterial road. Numbers 7 through 10 are labled "critical to very critical," and corresponding text notes that this typically involves: interstate, lifeline, some NHS, sole access, and no alternate routes. An accompanying photo shows an 8-lane divided highway. The graphic has a color sceme from cool colors on the left, starting with blue, through warm colors on the right, ending with deep red.

Figure 2: WSDOT Criticality Rating Scale

2.3.2 Criticality Assessment Resources

Assessing Criticality in Transportation Adaptation Planning, FHWA, 2011. This memo discusses approaches for narrowing the universe of transportation assets to study in a climate change vulnerability and risk assessment by assessing their "criticality" and otherwise narrowing study scope. It identifies common challenges, and draws on examples from the FHWA Adaptation Conceptual Model Pilots and the ongoing USDOT Gulf Coast Phase 2 study.

Assessing Infrastructure for Criticality in Mobile, AL: Final Technical Memo, FHWA, 2011. This memo summarizes the methodology and findings of Task 1 of the Gulf Coast Phase 2 study, which identified the transportation infrastructure components most critical to the Mobile region.

2.4 Identify Key Climate Variables to Study

An important first step to a vulnerability assessment is identifying which climate variables should be included in the study. Not all changes to the future climate will be significant to the local or regional transportation network, and limiting the study to the key variables of interest may allow for more in-depth projections of these variables. Section 3.3 includes more detailed information on developing climate information.

2.4.1 Key climate variables to consider

A range of future changes to the climate are of importance to transportation systems. Which ones are important to a specific transportation agency will vary by region and by study objectives. For transportation, the most important changes are often not changes to annual or seasonal averages, but to relatively short duration extreme events that can cause significant damage to transportation infrastructure or disrupt transportation operations. Examples of the kinds of climate changes included in transportation vulnerability assessments are broadly outlined below:

2.4.2 Selecting climate variables to study

The climate variables selected will most likely be influenced by agencies' experiences regarding the system's performance in the past in response to the local weather, especially during extreme weather conditions such as high winds, heat waves, flooding caused by heavy precipitation or coastal storms, or drought. Examining transportation system performance during historic weather events can aid in understanding the sensitivity of the transportation system to weather extremes and aid in selection of the climate variables and thresholds to examine in the projections, providing information that can be used to gauge impacts associated with future climate conditions.

An assessment of past weather-related disruption and damage may consider:

The historical information can provide a foundation from which to identify future vulnerabilities and the climate variables/thresholds that should be addressed in the projections. For example, if heat waves pose problems for transportation systems or assets, then the model projections for temperature during the spring, summer, and fall months should be investigated closely (increases in winter temperatures are unlikely to result in "heat waves" for most locations). A specific variable to consider might be the frequency of days over 95 degrees Fahrenheit in the future, which might affect restrictions on construction or operations work crews, or perhaps information on likely exceedances of the temperature threshold applied in a particular materials specification or guidance.

While these thresholds should inform the variables for which projections are run, it is also important to be mindful of the potential of climate effects previously experienced rarely, if at all. For instance, in coastal areas it may make sense to consider projections of sea-level rise even if sea levels or tides have not been a concern in the past. [See section 3.4 for additional discussion of climate sensitivity.]

2.4.3 Options for Obtaining Climate Information

One consideration in determining what climate variables to look at may be the availability of future climate data for your study area, given the resources at your disposal. Information on projected changes in climate can be obtained in several different ways, including:

Transportation agencies may want to partner with other groups that have experience developing or using climate projections. Useful sources of information and assistance include:

2.4.4 Examples from Practice: Identifying Climate Variables for Study

The differing objectives of the pilot studies resulted in a range of approaches:

Table 1:

Climate Variables Used in the Gulf Coast Phase 2 Study

Variable Mode Analysis
Annual, seasonal and monthly precipitation Multi Pavement design
Annual, seasonal, and monthly average minimum, maximum, and mean temperature Airports Runway design
Daily high temperature: mean, 50%, 95%, and warmest day in the year during each 30-yr period Rail AREMA rail design/ buildings
Seasonal and annual number of days and maximum consecutive days of high temperatures at or above 95oF, 100oF, 105oF, and 110 oF Civil/Geotech/ Pavement Comparing high temp days' duration to existing design standards
Mean, 5%, 25%, 50%, 75%, 95%, and largest occurrences for the average minimum air temperature over four consecutive days in winter, and the average maximum temperature over four consecutive days in summer Bridge /Rail Comparisons to AASHTO recommendations
Mean, 50%, 90%, 95%, and 99% occurrence of the coldest day of the year during each 30-yr period Multi Pavement design
Maximum 7-day average air temperature per year with the % probability of occurrence during each 30-yr period (mean, 50%, 90%, 95%, 99% occurrence) Multi Pavement design (asphalt)
Exceedance probability precipitation for 24-hour period with a 0.2%, 1%, 2%, 5%, 10%, 20%, and 50% exceedance precipitation events (e.g., 500-yr, 100-yr, 50-yr) Multi Drainage/liquid storage
24-hour exceedance probabilities based on today's 0.2%, 1%, 2%, 5%, 10%, 20%, and 50% exceedance precipitation events Multi Drainage
Exceedance probability precipitation across four consecutive days: 0.2%, 1%, 2%, 5%, 10%, 20%, 50%, mean; Exceedance probability of precipitation across two consecutive days: 0.2%, 1%, 2%, 5%, 10%, 20%, 50%, mean Pipeline Historical analysis of inundation
Largest 3-day total of precipitation each season Multi Change in storm events

2.4.5 Resources for Identifying Key Climate Variables

Regional Climate Change Effects: Useful Information for Transportation Agencies, FHWA 2010. This document provides basic information on projected future climate change effects over the near term, mid-century and end-of-century by U.S. region.

The Use of Climate Information in Vulnerability Assessments, FHWA 2011. This memorandum focuses on the use of climate information when performing a vulnerability assessment. The memorandum includes discussion of using historical climate information and includes information on potential data sources.

Updated: 03/27/2014
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