Don't Forget to Collect High Water Marks Data After a Flood Event

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The Importance of Collecting High Water Mark Data After a Flood Event​

Flood events can cause significant damage to communities, and understanding the extent and impact of such events is crucial for effective floodplain management and disaster response. Collecting high water mark (HWM) data after a flood provides critical information that helps assess damage, supports recovery efforts, and informs future mitigation strategies. This article will outline the importance of collecting HWM data, how to collect it, and how it can be used to enhance community resilience.

Why Collect High Water Mark Data?​

1. Assessing Damage Extent and Severity:
   • HWM data provides a clear indication of the maximum flood level reached in various locations, helping to identify the most severely impacted areas. This information is vital for prioritizing emergency response and recovery efforts.
2. Supporting Disaster Declarations:
   • Accurate HWM data is essential for conducting Preliminary Damage Assessments (PDAs), which are used to justify requests for state and federal disaster declarations. These declarations unlock funding and resources necessary for recovery.
3. Enhancing Floodplain Management:
   • Understanding flood patterns and water levels helps in updating floodplain maps and revising local floodplain management regulations. This ensures that new developments are better protected against future flood risks.
4. Informing Mitigation Efforts:
   • HWM data can be used to apply for mitigation grants aimed at reducing future flood risks. This includes funding for elevating buildings, constructing flood barriers, and other flood-proofing measures.
5. Community Planning and Resilience:
   • By documenting the extent of flooding, communities can plan for better infrastructure and emergency response strategies. This includes improving drainage systems, building higher bridges, and creating evacuation plans.

How to Collect High Water Mark Data​

Collecting HWM data requires a systematic approach to ensure accuracy and usefulness. Here are the general steps for collecting HWM data:

1. Target Locations of Significant Flooding:
   • Focus on areas where flooding was most severe. Look for visible indicators such as mud lines, debris, and water stains on buildings, utility poles, trees, and other structures.
2. Identify and Document Locations:
   • Record the precise location of each HWM using building addresses and GPS coordinates. This helps in creating an accurate map of flood levels across the affected area.
3. Mark and Measure Water Levels:
   • If possible, place a permanent marker at the high water mark on structures. Measure the height of the mark above the ground and record the measurement.
4. Photograph Evidence:
   • Take photographs of the HWM, ensuring both a close-up of the mark and a wider shot showing the surrounding area for context. Include identifiable features such as building numbers or street signs.
5. Record Detailed Data:
   • Maintain detailed records, including the date of data collection, the person collecting the data, and any additional notes about the location and the conditions observed.
6. Upload Data to a Centralized System:
   • Use tools like the Florida High Water Mark Mobile Reporting System to upload data in real time. This ensures that all collected data is stored in a centralized, accessible database for future reference.

Utilizing High Water Mark Data​

Once collected, HWM data serves multiple purposes:

• Supporting Damage Assessments:
  • HWM data helps validate claims of flood damage, providing a basis for estimating repair costs and determining eligibility for federal assistance.
• Informing Substantial Damage Determinations:
  • Floodplain administrators can use HWM data to make determinations about whether buildings have sustained substantial damage, which may require compliance with current floodplain management regulations.
• Improving Future Flood Response:
  • Analyzing HWM data from past events helps improve flood response strategies and emergency preparedness plans, ensuring better protection for communities in future flood events.

TBCF Summary​

Collecting high watermark data after a flood event is a critical task for floodplain administrators and building officials. This data not only aids in immediate disaster response and recovery efforts but also plays a key role in long-term floodplain management and community resilience. By following systematic procedures for collecting and documenting HWM data, communities can enhance their ability to mitigate future flood risks and ensure the safety and well-being of their residents.

For more detailed guidelines and tools for collecting HWM data, refer to the resources provided by the Florida Division of Emergency Management and FEMA.