Each year, Delaware experiences anywhere from 10 to 35 significant coastal storms, including nor’easters and tropical systems. These storms bring with them the potential for coastal flooding, one of the most significant natural hazards facing the state today.
In 2012, for example, Superstorm Sandy brought strong winds and nearly five feet of storm surge along Delaware’s coast, setting records at many of Delaware’s tidal gauges, while dropping more than 10 inches of rain near Rehoboth Beach and six inches of rain or more across New Castle County. The storm led to power outages, highway closures and flood damage throughout the state.
Other recent storms to significantly affect Delaware include Hurricane Irene in 2011 and the Mother’s Day storm in 2008.
University of Delaware researchers in the College of Earth, Ocean, and Environment are developing a centralized database and website to capture flood data in an effort to better understand and document the extent and severity of flooding in Delaware. In particular, the research team is focusing on data related to high water marks (HWM), the maximum level reached by the sea at high tide, or by a lake or river at its highest stand.
“Where coastal flooding occurs, how it occurs, and the depth and timing of flooding are all important issues,” explained John Callahan, associate scientist with the Delaware Geological Survey and principal investigator on the project.
“Several Delaware organizations collect high water mark and peak storm tide data but until now there has been no centralized infrastructure to manage, collaborate and share this information effectively.”
Collaboration is key
HWMs are typically observed as water stains on buildings, debris lines on streets or beaches, or changes in vegetation appearance. They are generally considered the best method for capturing the maximum depth and extent of a flood, and provide important information for disaster recovery planning and allocation of insurance claims.
Additionally, they are useful for evacuation and safety planning and for calibrating hydrodynamic models.
Fieldwork to identify and document HWMs, however, is time consuming and requires trained staff. It must be performed shortly after an event when other tasks typically take priority.
With funding from Delaware Sea Grant, Callahan and a team of researchers will create the technical infrastructure needed to:
- Maintain and distribute both historical and future storm HWM data;
- Increase the spatial coverage of flooding by deploying numerous automated water level sensors in vulnerable areas prior to a storm; and
- Facilitate the groundwork for improved multi-agency collaboration and information sharing regarding coastal flooding in Delaware.
According to Callahan, the deployment of monitoring sensors before an event and subsequent fieldwork afterward are best performed in coordination with other agencies doing similar work.
Collaborating agencies on the project include the U.S. Geological Survey and the National Weather Service, and local county and state partners such as New Castle County, the Delaware Department of Natural Resources and Environmental Control (DNREC) and the Delaware Emergency Management Agency, among others.
Co-principal investigators involved in the UD project are:
- Kevin Brinson, director, Delaware Environmental Observing System (DEOS);
- Hunter Brown, operations manager, UD Robotic Discoveries Laboratories;
- Christina Callahan, lead scientist, Delaware Environmental Monitoring and Analysis Center (DEMAC); and
- Dan Leathers, state climatologist and professor in the Department of Geography.
Christina Callahan from DEMAC will develop and host the database and support a public website for HWM and peak storm tide data. The interactive website will include maps of maximum water levels at many observation locations throughout Delaware.
Participating agencies will be able to contribute, and use, the information.
Educational tools for identifying and documenting high water marks, including how the information is recorded (paper, tablet, phone), may also evolve from the project.
Bringing constituents together
In November, the research team hosted a workshop for local, county, state and federal constituents to discuss how HWM data currently is captured and to discuss ways to improve data sharing and pre- and post-storm activities. The workshop took place at the Delaware National Estuarine Research Reserve St. Jones Training Center in Kitts Hummock.
“Coordination is a large part of the project. The willingness of our partners to collaborate and share information is helping us create an online repository for data that previously was stored in books, reports and on computers. We are building something that will be useful, now and into the future,” said John Callahan.
Monitoring efforts for future storms will focus on high-risk areas and those areas most vulnerable to a particular flood event. Working with partner agencies, Brinson will select sites to deploy mobile sensors during future storm events.
“We want to place our sensors in gap areas — sites not currently monitored by other agencies — to achieve the best possible coverage statewide,” said Brinson.
The pressure-based sensors run on long-lasting lithium batteries and measure and record water depth at various intervals (minutes, hours) for several months before data collection is required. The measurements will be used to determine water surface elevation and extent throughout the affected areas. Multiple measurements over time will allow the researchers to account for disparities due to tides, winds and other factors.
“In terms of total dollars, damage, risk and recurrence, flooding is the number one environmental hazard that Delaware faces year in and year out,” said Brinson. “Documenting and understanding flooding is something we as a state have not done sufficiently. This project to document high water marks is one piece in completing that puzzle.”
Article by Karen B. Roberts
Photos by Evan Krape and courtesy of Delaware Sea Grant