Hurricane Ian Study

Objective
Conduct a research study on Hurricane Ian’s 2022 landfall in Florida to:

1. Improve (a) coastal flood hazard characterization, including quantification of overland velocity and waves, (b) quantification of storm surge loads on buildings due to hydrostatic pressure, wave forcing, surge velocity, and debris impacts; and (c) guidance on these loads for existing building codes and standards.
2. Improve understanding of differences in meteorological and engineering estimates of hurricane wind speeds at landfall, document successes of recent improved building structural wind resistance codes and standards, and identify shortcomings in existing codes and standards in preventing loss of building function due to nonstructural damage due to wind and wind-driven rain.
3. Improve emergency preparedness and response practices by examining the emergency communications and evacuation actions taken along the southwest Florida coast.

Technical Idea
STORM SURGE PROJECT: The significant storm surge damage caused by Hurricane Ian highlighted weaknesses in how current codes and standards address this hazard. ASCE-7 and ASCE-24 provide provisions for surge loads, but these may be underestimates as they do not adequately consider hydrodynamic effects caused by flow velocity and wave actions, which are not mapped, and subsequently there is insufficient engineering guidance. More research is needed to validate and improve these standards, and this project will include two key efforts:

• Develop improved understanding of coastal flooding – overland currents and waves in the built environment, hazard characterization (e.g., return periods), and uncertainty quantification.
• Develop improved understanding of hydrodynamic loadings on buildings and infrastructure – validated models and equations for wave/surge loads.

WIND PROJECT: Engineering estimates of the maximum peak gust wind speeds near landfall were in the range of 120-130 mph, based on a combination of anemometry measurements and modeling.  In comparison, sustained wind speeds (over water) at landfall were estimated at 150 mph (NHC 2022), which is equivalent to 165 mph peak gusts over land.  This difference between land-based observations/engineering assessments and meteorological estimates has been noticed in most significant hurricanes in recent years.  Hurricane Ian provides an opportunity to uncover the root cause of these differences in wind speed estimates. In addition, asphalt shingles have been observed to repeatedly fail at below design wind speeds, in this event and others. Massive losses in this event resulted from water intrusion caused by non-structural wind damage, such as roofing damage. Hurricane Ian provides an opportunity to document the effectiveness of secondary water intrusion barriers required by more recent versions of the Florida Building Code. Improvements to current codes for asphalt shingle materials and testing and a better understanding of the relationship between non-structural damage and water intrusion will help reduce significant economic losses. More research needs to be done to reduce these kinds of losses in the future, and this project will include five key efforts:

• Understand why land-based wind speed observations are often 20-30 mph less than reported wind speeds at landfall based on offshore and nearshore observations.
• Study the duration of the wind speeds extreme and wind directional changes over short periods of time along with the translational speed of the hurricane to understand the stresses upon the buildings.
• Understand performance of recently improved wind resistance codes and standards as it relates to secondary moisture barriers (FBC R908.7.2).
• Understand the role of potential age-related sealant failures in the loss of asphalt shingles at below design wind speeds.
• Understand causes and impacts of water intrusion including loss of building function.

EMERGENCY COMMUNICATIONS PROJECT: Low evacuation rates led to increased fatalities in Hurricane Ian, which prompts the questions as to why people chose not to evacuate, and how could emergency communications be improved in the future to be more effective?  This research will dovetail with components of the ongoing Hurricane Maria investigation and builds on past work from other NIST-led NCST investigations. This study will improve emergency preparedness and evacuation in future hurricanes to reduce loss of life, and will include one key effort:

• Understand causes of the low evacuation rate along the SW Florida coast
• Understand the role of perceptions of building safety and accuracy of those perceptions in evacuation decision.
• Include income into the study of the evacuees or non-evacuees

Research Plan
Many investigations to develop codes and standards for building loads from wind, wave and surge      have been completed, but the implementation work needs to continue. Developing case studies and validation of current generation models to ensure improved performance of hurricane effects for future events is essential.  A NIST-sponsored and organized workshop on Hurricane Ian Data Synthesis was held at ASCE HQ in 2023, where participants presented on data they have collected, with an emphasis on supporting building load performance studies for storm surge and wind.  The workshop results are documented in a NIST (2025) report.  This provides a comprehensive baseline on the state of the data collection activities on Hurricane Ian as of 2023.  A second workshop will be held in spring 2025, with a report delivered later in 2025.

STORM SURGE PROJECT: The storm surge project will focus on two key research areas:

• Coastal flood hazard characterization
  • Develop new sensors and measurement approaches to observe currents and waves during storm surge flooding over land.
  • Validate existing storm surge and wave models with existing data from Hurricane Ian that have been previously collected (mainly high-water marks) and from future events including current and waves.
  • Identify knowledge gaps that still need to be addressed, by comparison with field measurements, to demonstrate that the models are sufficiently accurate to use as a basis for defining hurricane-induced environmental conditions to specify appropriate building standards in the coastal zone.
• Hydrodynamic loads on buildings and infrastructure
  • Validate existing approaches and equations for hydrodynamic loads on buildings and infrastructure
  • Develop more sophisticated load hydrodynamic drag models including distribution of forces on the structure
  • Develop appropriate load equations for hydrodynamic uplift on structures

WIND PROJECT: The wind project will develop case studies and validate existing research cases in four key research areas:

• Develop explanations for the frequent significant differences between surface-level winds in landfalling hurricanes based on offshore observations and onshore observations.
• Document the impact of new codes on water intrusion–verify performance of current codes and any benefits, and determine whether, and how well, secondary moisture barriers work.
• Explain the failure of asphalt shingles at below design wind speeds, and especially the relationship with age of roof–study potential mechanisms of sealant degradation and the effectiveness of current test methods.
• Understand the stresses on the built environment due to the time duration of extreme wind speeds and sharp/rapid wind directional change during the hurricane event.

A detailed literature survey will be conducted to help understand the different procedures, datasets, definitions, assumptions and operational analyses underlying surface-level marine and onshore wind speed observations and estimates in landfalling hurricanes. This will be followed by a workshop with key meteorological and engineering stakeholders from the government, academia and private sector, to examine the measurement science issues. A key goal will be to identify if there is a greater reduction in wind speeds happening in landfalling hurricanes compared to the standard models for transition of winds from marine to overland exposure and develop research plans to answer this question.

The project will also include an extensive literature review focused on water intrusion related to wind-driven rain (WDR), and quantifying the prevalence, causes, and impacts of WDR in both experimental and real-world conditions. Literature on the role of post-disaster imagery as a means of exploring WDR will be analyzed. Collected imagery will be used to examine the prevalence of WDR water intrusion post-Ian by looking for debris piles placed for trash pickup that contain interior contents.  This will involve locating appropriate communities that did not experience flooding that have post-event imagery available for analysis.  Focus will be paid to buildings constructed post-2020 due to an update to the Florida Building Code that required the use of secondary moisture barriers for many residential homes allowing for a comparison against homes built prior to gauge the effectiveness of the code change. There will be an additional focus on structures showing little to no damage as any evidence of water intrusion is likely to be due to WDR intrusion.  As this type of analysis seems to be novel, the research will also contain an examination of the methodology’s benefits and limitations in the current case, as well as recommendations for data collection in support of the method.

Related work on asphalt shingles will begin with a literature review on the current state of knowledge concerning the frequency of failure, especially in below-design wind events, the mechanisms of asphalt shingle failure and any field or experimental work done trying to identify or model failure paths. Relevant standards will be determined as well.  Sealant related issues will also be researched including the typical sealants used, issues related to aging or fatigue and real-world performance.

EMERGENCY COMMUNICATIONS PROJECT: The evacuation and emergency communication study will begin with a review of data collected from other groups and agencies before proceeding to collect additional data. Consideration will have to be given to the span of time from the event to the data collection period and what impact that may have on the study.  Also, this study may include other storms to help set context from storms with a spectrum of forecast confidence and emergency messaging.  The emergency communications project will focus on four key research areas:

• Evaluate evacuation decision-making processes by residents based on
  • hazard communication attributes and sources
  • existing data collected by U of AL, FEMA, NHC, StEER, and others
  • metadata analysis of existing data
• Study the influence of shelter/home attributes on evacuation decisions by collecting data on
  • the structural integrity of the residences of interviewees
  • interviewees’ perceptions of their homes’ performance as a shelter
  • forensics analysis of same structures from past data and new events
• Develop recommendations for improving evacuation communications to recipients
• Contextualize the results from Hurricane Ian with other storms