CHAPTER 4

Operations

Key Focus

Using flood forecasts to inform proactive and coordinated responses to flooding events.

Key Takeaways

• Important sources of information needed when evaluating response options include:
  • Emergency action plan protocols,
  • Feedback on the ground,
  • Gauge data crossing flood risk thresholds, and
  • Interdepartmental communication.
• DOTs currently rely on flood forecasts to inform actions such as issuing internal flood level notifications, directing field staff to flood locations, and issuing road closures.
• Uncertainty must be accounted for in decision-making, and field validation can support building confidence in forecasts.
• Establishing protocols to record impacts after a flooding event can support improved monitoring and response for future events.

Actions to Accomplish

• Determine what sources of information will be used to inform specific response actions.
• Establish roles and communication channels between the state DOT and district/regional offices for field validation of conditions and actions taken.
• Establish a risk tolerance for priority assets to support decision-making during a response.
• Identify information to be collected from operational response experiences (such as closure locations, durations, and high-water marks) in ways that are findable, accessible, interoperable, and reusable.

4.1 Overview

In the context of a flooding event, operations refer to DOT processes to execute a coordinated response to maintain transportation infrastructure level of service. Figure 4-1 highlights mature operations capabilities.

4.2 Introduction

When a flooding event occurs, DOTs play a critical role in a coordinated response that supports public safety and operations personnel. This chapter will focus primarily on the steps taken during a flooding event, drawing from case studies and examples of existing DOT operational capabilities and how flood forecasts can be leveraged through the process. Flood forecasting response will look like preemptively convening key personnel to discuss potential impacts so that when an event occurs, an action can happen in a timelier and more prepared way. In contrast, response without flood forecasting may rely on responding to observations or making last-minute changes.

DOTs that want to start flood forecasting will find information on how to use flood forecasting to inform decision-making during a flooding event. DOTs that already flood forecast

but want to build or advance capabilities will find tools and resources to support enhanced effectiveness in responding to flooding events.

A mature flood operations capability will include:

• Proactively informing emergency response actions for roadway flooding impacts,
• Efficiently establishing detour routes, and
• Recording local and institutional knowledge.

This chapter is organized into the following sections to cover how DOTs may begin or expand their operational capabilities.

• Connecting Forecasts to Action. Provides an overview of the types of actions flood forecast information can inform and key questions to support building emergency response plans.
• Response During a Flood Event. Describes existing structures for coordinated response during a flooding event and a case study on how to leverage multiple sources of information.
• Recording Flood Impacts. Identifies opportunities to streamline and enhance processes for recording impacts following a flood event.

4.3 Connecting Forecasts to Action

During a flooding event, DOT operational functions generally include responding to flooded roads and establishing and communicating detours in road closures. The Federal Emergency Management Agency (FEMA) further defines emergency support functions for DOTs to include monitoring and reporting damage and status of the transportation system and infrastructure; identifying temporary alternative transportation solutions if systems are damaged, unavailable, or overwhelmed; and coordinating across multiple transportation stakeholders before, during, and after the event response. Flood forecasts can support a coordinated and proactive approach to hazard response operations by providing better lead time for events, enabling more efficient use of resources, and supporting faster response in the field.

In the survey of participating study DOTs, respondents indicated that they use flood forecasts primarily to:

• Disseminate internal flood level notifications,
• Direct field staff to flood locations, and
• Issue road closures.

According to the survey respondents, the most frequent sources of information used to inform key actions are regular weather forecasts, stream gauge thresholds, citizen reporting, and history of flooding at a location, as shown in Figure 4-2. For example, Missouri DOT uses thresholds based on previous flooding events to determine when water levels will likely result in a road closure requiring field staff interventions. However, changes to land use and climate conditions, watershed drainage, rainfall intensity, and rainfall frequency are ongoing. These changes may, in turn, result in changes to event timing and impact from historical experiences. For example, a historical time to peak of 6 hours once a gauge hits a certain threshold may now occur in 3 hours. Operation in such a dynamic environment further necessitates robust capture of such event attributes to enhance future response activities and identify emerging trends.

Emergency management protocols and response plans are important for connecting flood forecast information to specific actions. These plans may be used to document how a DOT will

respond to a flooding event under specific weather conditions and the subsequent activities following an event. For example, Colorado DOT (CDOT) has created emergency response plans for critical transportation corridors, such as the US-24/Waldo Canyon Burn Corridor Updated Emergency Response Plan (Colorado Department of Transportation 2018). As shown in Figure 4-3, CDOT has established specific response triggers to inform the decision of when to implement a roadway closure on US-24. Using six USGS rain gauges along the Waldo Burn Scar, CDOT maintenance supervisors monitor daily and past 5-day cumulative rainfall in the area. NWS, local weather forecasts, and CDOT cameras along the US-24 corridor also assist in monitoring road conditions. Suppose that there is a USGS 5-day cumulative rainfall greater than or equal to 2 inches at any monitored rain gauge or that NWS issues a flash flood warning. In that case, an initial response is triggered with mobilization of resources by CDOT and the Colorado State Patrol. If flooding is imminent or has occurred and requires a roadway closure, the US-24 Waldo Burn Corridor will be closed immediately, and preestablished messaging will be activated to warn the traveling public (Colorado Department of Transportation 2018).

Leveraging flood forecasts in DOT operations can help inform a more strategic approach to deploying temporary flood countermeasures and issuing road closures. DOTs have existing communication channels to communicate flood forecast results quickly, and DOT survey respondents indicated that it typically takes less than one hour to communicate forecast results. While this supports a quick response to flooding conditions, integrating a flood forecasting capability in an emergency response plan can help support more proactive decision-making. Building on the CDOT example, the following key questions can assist DOTs in developing or enhancing their emergency response plans.

• What is the risk tolerance for different transportation assets?
• How are priorities for response established if multiple assets are affected?
• What thresholds indicate when additional monitoring is needed versus a road closure?
• Who will be responsible for responding to the flood event once trigger conditions are met?
• If one roadway or bridge is closed, how does this affect the transportation network, and what detour routes are available?
• How will the DOT communicate to partner agencies about issues such as road closures and detours?
• What methods are used to determine when it is safe to re-open a roadway?

CDOT

CDOT has created emergency response plans for critical transportation corridors, such as the US-24/Waldo Canyon Burn Corridor Updated Emergency Response Plan.

4.4 Response During a Flood Event

DOT response to transportation asset flooding involves coordination across multiple levels of government. While emergency management within the DOT often leads the response, DOTs also indicated in the survey that maintenance (83% of respondents) and specific districts/regions (66% of respondents) also play an integral role in decision-making processes. In a decentralized response model, district or regional offices lead monitoring efforts of roadway conditions and relay critical observations to a centralized state office to identify additional resources needed. In a centralized model, the state office will provide guidance on where district or regional personnel should be deployed to monitor roadway conditions. Under either of these scenarios, efficient communication between the region and state is important.

NCDOT has a robust operations process for responding to flooding events that integrates information from multiple platforms. The North Carolina Flood Inundation Mapping and Alert

Network (FIMAN) is a public-facing platform used to monitor gauges and flood conditions (North Carolina Department of Transportation 2023a; see Figure 4-4). FIMAN-T is a layer added onto FIMAN specifically for transportation and is used to predict estimated flood depths on roads and bridges. During a flooding event, the state office shares FIMAN-T road inundation summary reports with divisions as information becomes available for predicted maximum-event impacts. These summaries include information on predicted flood stage, flood timing, and roadway miles inundated within each county. NCDOT also uses BridgeWatch to monitor thresholds for flooding response (for more information on BridgeWatch, see Chapter 3). Once a preestablished threshold has been triggered by a BridgeWatch sensor, Traveler Information Management System (TIMS) managers will be notified and the county/division will be contacted. Following field verification, the road will be closed if needed. All flood data are verified before being added to DriveNC.gov (North Carolina Department of Transportation 2023b), the public-facing site that communicates traffic information (see Figure 4-4).

In the event of a road closure, detour routes are essential to maintaining DOT customer mobility and the functioning of the transportation network. By establishing detour routes for areas of frequent flooding before an event, flood event response can be streamlined. For example, Virginia DOT (VDOT) has established a procedure and guidelines for planning, designing, and implementing incident detour plans (Virginia Department of Transportation 2020a). With one overall template to address VDOT and public safety priorities when an incident detour is implemented, personnel involved in event response have a common design and format to help enable a more efficient response. The incident detour plan template includes traffic control posts, detour routing instructions, applicable changeable sign messages, pre-identified coordinating agencies, and a supporting map.

DOT response to more severe flooding events, such as hurricanes, may involve engagement with external partners to establish emergency operations centers (EOCs), where emergency operations are directed and coordinated across multiple agencies. For states that use EOCs, decision-makers and support agencies will supervise the coordination of response activities, such as evacuation (Federal Highway Administration 2012). While EOCs are often temporary, Transportation Management Centers (TMCs) are permanent entities that can coordinate with EOCs during an emergency event. TMCs monitor roadway conditions, provide support to motorists and responding field personnel, and actively manage traffic flow. For example, the Washington State Department of Transportation (WSDOT) TMC continually monitors inclement weather and road conditions using hundreds of cameras on the state highway system and data from traffic detectors. WSDOT TMCs also convey information to the traveling public across multiple platforms, including WSDOT real-time travel data web pages (Washington State Department of Transportation 2021).

TMCs can serve an important role in emergency response by proactively monitoring roadway conditions in anticipation of weather events, managing detours and evacuation routes, and facilitating communication with local transportation agencies and the public.

4.5 Recording Flood Impacts

Documenting the impacts of flood events can support future flood modeling and response efforts and can identify assets damaged by flooding. Survey respondents indicated that current flood impact recording processes are based on field observations that are recorded or shared through an internal database, cross-departmental communications, and region- or district-wide forms. Setting up consistent flood impact recording processes facilitates ease of information sharing across regions and events and reduces the data processing required to incorporate recorded flood impacts into a more extensive monitoring database.

Some federal, state, and local agencies have established approaches to recording flood impacts. At the federal level, the NWS provides information on observed flood impacts associated with specific flood levels at monitored gauge locations (National Weather Service 2023). At the state level, examples of practices for recording flood impacts include the following:

• New Jersey DOT (NJDOT) uses unmanned aerial systems (UASs) for survey and data mapping, including during emergency response events like floods. NJDOT’s UAS also supports structural inspections, traffic congestion management, and watershed surveys (New Jersey Department of Transportation 2021).
• TxDOT relies on district offices for flood monitoring, and each district has at least one maintenance office per county. These maintenance offices have teams that are responsible for recording flood stage levels based on visual and physical on-site inspection. When crossings or roadways flood or are close to overtopping, the maintenance office teams add the data to the Highway Condition Reporting System (Park et al. 2021).
• Pennsylvania DOT (PennDOT) uses post-flood inspection reports to record flood conditions and impacts for bridge assets. These reports are generated following alert notifications from the PennDOT BridgeWatch system and include field images and key information such as the event date, resulting damages, and if bridge overtopping occurred or closure was required (Pennsylvania Department of Transportation 2022).

At the local level, the city of Nashua, NH, leveraged crowdsource information on flooding to support the development of the city’s Hazard Mitigation Plan. Crowdsourcing information during flood events can be a valuable way to identify areas experiencing flooding at the local level. Standardizing crowdsourced information may be more challenging than relying on staff input, but it can supplement other methods of recording flood impacts (Kates 2022).