Flood Intel Unit (FIU)

What is a flood monitoring network?

Flood monitoring networks can save lives and prevent or mitigate damage to property and infrastructure. Networks accomplish these goals by observing rainfall accumulation and monitoring water levels then alerting the appropriate channels when conditions approach either imminent or forecasted impactful levels. An effective network enables public safety stakeholders to take appropriate action in advance of a flood event such as evacuations and road closures, which often leads to less catastrophic outcomes when severe weather strikes. This valuable flood monitoring and risk mitigation is achieved through a network of remote sensor stations installed at strategic locations within a watershed or over a body of water.

Why is the FIU network so important?

Our gage network is important because it affords us to observe near real-time data to influence better prediction of downstream affects. These predictions and early warnings help keep Virginians safe - especially in underserved communities that may lack observational data to support residents and public safety officials.

Some examples of historical, catastrophic flooding events you might be familiar with include:

• Hurricane Camille – August 1969
• Tropical Storm Agnes – June 1972
• Madison County Flash Flood – June 1995
• Hurricane Fran – September 1996
• Tropical Storm Isabel – September 2003
• Tropical Storm Matthew – October 2016
• Spring Floods, North/Northwest VA – April-June 2018
• Tropical Storm Michael – October 2018
• Buchanan County Flash Floods, August 2021 and July 2022

Many of these events were difficult to detect or forecast well in advance due to observational gaps in data from federal, local, and private network observing systems. These gaps are prominent in many smaller or resource-disadvantaged communities that often experience disproportionately high impacts during high-impact flood events.

In the western regions of Virginia, steep terrain and deep valleys alternate to produce numerous micro-climates, each potentially different from the broader regional picture. The central Virginia urban corridor encompasses higher population density which can make a small shift of location in a forecasted rainfall event affect a significant amount of people and higher amounts of critical infrastructure. Eastern and coastal Virginia possess thousands of miles of coastline and numerous small towns, all uniquely at risk of tidal flooding, flash flooding, and storm surge.

Having our own network of hyper-local monitoring sites that provide rapid data outputs will make it substantially easier to have increased awareness of hydrologic risk and therefore, strengthen our ability to provide more accurate predictions and better, more customized warnings to stakeholders.

Public officials can remotely monitor gages in areas affected by potential flooding to help assess, coordinate, and implement road closures, enhance personnel safety, issue evacuations, and more. Residents and businesses can also monitor water levels in the vicinity to assist in understanding if they will be affected by flooding and to hopefully take appropriate actions to mitigate damage. Ultimately, a gage is equally as useful to citizens as it is to public safety officials.

Additionally, these gage sites will provide a short- and long-term repository of statewide hydrologic information which has obvious benefits for scientific and research purposes. These benefits include documentation for State or Presidential Disaster Declaration requests and National Flood Insurance Program Community Rating System discounts. In learning from other state’s successful flood monitoring networks such as North Carolina and Iowa, Virginia is poised to implement a cutting-edge network that will provide a plethora of benefits to its citizens and stakeholders.

What are the components of the gage sites?

Integrated Data Logging System

An integrated data logging system is a real-time monitoring station that houses the data logger, telemetry module, and power/charging supply. Since it is generally cost-prohibitive to run AC power to the monitoring location, integrated solar panels are used to continuously charge the 12V-DC battery for autonomous operation.

Mounting Hardware

Water-level gages will be mounted to infrastructure such as VDOT or jurisdiction bridges or culverts, and rain gages will be mounted on tripods.

Ultrasonic or Radar Water-Level Gage

VDEM utilizes non-contact gages to measure water level. Non-contact gages are mounted above the water, typically on a bridge, and measure the distance from the gage to the water’s surface. These types of gages have a proven track record of lower maintenance, reduced failure occurrences, and the elimination of sensor “fouling” or “clogging” compared to submersible sensors.

Radar Precipitation Gage (Rain Gage)

VDEM utilizes a rain gage with radar technology. Using a 24-GHz Doppler radar, the sensor measures the speed of all forms of condensed water (rain, freezing rain, hail, snow, and sleet). The low-energy sensor detects precipitation from the first drop and importantly measures precipitation intensity. The equipment is nearly maintenance-free through ingenious technology without any moving parts.

Telemetry

LTE and Satellite are the primary means of communication. VDEM utilizes gages supported by wireless two-way transceivers which:

supply and regulate gage power

report environmental data

report device health data

receive and act on commands from the cloud platform

How will the data collection occur?

The National Weather Service operates a system called the Hydrometeorological Automated Data System (HADS). This is a real-time data acquisition and data distribution system operated by the National Weather Service Office of Dissemination. Once data is logged, it auto-reports to NWS and is shared with personnel at the Weather Forecast Offices, River Forecast Centers, National Water Center, data analytics tools, and the broader weather enterprise. This will greatly enhance real-time awareness to ground-truth radar observations and strengthen the confidences of flood and flash flood watches and warnings.

How will the data improve real-time awareness and NWS forecasting?

By filling critical observation gaps, VDEM can help create a larger and more detailed picture of the hydrologic environment with fewer blind spots and more frequent data collection points. This enhanced information means we can spot more fine-scale events as they happen, especially in more rural/remote areas, better predict when events are likely to happen, and provide more accurate information to local personnel responsible for assisting during emergencies.

Is the data going to be publicly available?

Yes, all VDEM-collected data can be viewed via the NWS National Water Prediction Service website

How many new gage sites will be installed?

The current project encompasses 136 new gages across the Commonwealth. If all goes smoothly, the project is expected to be complete by the end of Summer 2024. The FIU hopes to continue to add supplemental gages as high-risk data gaps are identified.