Flooding

Floods are natural disasters that occur when an area experiences an overflow of water onto normally dry land. These events can result from various causes and have significant impacts on communities, the environment, and infrastructure. Here are key aspects of floods:

Causes of Floods

1. Heavy Rainfall: Prolonged and intense rainfall can lead to the saturation of soil, exceeding its capacity to absorb water. This runoff contributes to surface water accumulation and potential flooding.

2. Storm Surges: Coastal areas can experience flooding due to storm surges, which are abnormal rises in sea level generated by storms, especially tropical cyclones.

3. Snowmelt: Spring thaw or sudden warming can cause the melting of snow, leading to increased water runoff and the potential for river or urban flooding.

6. Dam or Levee Failures: Failure of dams or levees can release large volumes of water, causing downstream flooding.

Types of Floods

4. Flash Floods: Flash floods result from intense rainfall over a short period, often in mountainous or urban areas. They can lead to rapid and unexpected rises in water levels.

5. River Flooding: Overflow of rivers and streams due to excessive rainfall or the melting of snow in upstream areas can lead to river flooding.

• Coastal Floods: Result from storm surges, high tides, or tsunamis, causing seawater to inundate coastal areas.
• Urban Floods: Occur in urban areas due to inadequate drainage systems overwhelmed by heavy rainfall.
• Pluvial Floods: Also known as surface water floods, these happen when heavy rainfall creates a flood event independent of an overflowing water body.

Impacts of Floods

1. Infrastructure Damage: Floodwaters can damage roads, bridges, buildings, and other infrastructure, disrupting transportation and utilities.

2. Loss of Lives and Property: Floods pose a significant risk to human life and property. Rapidly rising water levels can lead to evacuations and, in severe cases, loss of life.

3. Economic Impact: Flooding can have long-term economic consequences, affecting agriculture, businesses, and communities. Recovery efforts can be costly.

4. Environmental Consequences: Floods can alter ecosystems, impact wildlife, and introduce pollutants into water bodies, affecting the environment.

5. Public Health Risks: Contaminated floodwaters can pose health risks, including the spread of waterborne diseases.

Flood Data Analysis

Dataset	Description	Link
National Risk Index (NRI)	NRI is a dataset and online tool built by FEMA to help illustrate the risk of United States communities for 18 natural hazards. It was calculated expected annual loss resulting from hazards times social vulnerability and then divided by resilience. Both composite index of all 18 hazards as well as index for each individual hazard are given. Social vulnerability and community resilience information are also given.	Link
FEMA Flood map	FEMA provides flood maps for people to understand the flood risk of their community. The map can be accessed via an online viewer.	National Flood Hazard Layer Viewer
U.S. historical flood risks and costs	An interactive data tool to understand the flood cost. Flooding cost data is estimated using insurance claims from National Flood Insurance Program (data website) and FEMA's Individuals and Households Program (data website), which is also available for downloading.	Link
FEMA web disaster summaries	This dataset contains financial assistance values, including the number of approved applications, as well as individual, public assistance, and hazard mitigation grant amounts.	Link
OpenFEMA Dataset	FEMA also provides many other open datasets on disaster information, emergency management, assistance, hazard mitigation etc. in industry standard, machine-readable formats.	Link
NOAA historical flood events
Climate Risk and Resilience Portal Data Group	Dynamical downscaled future climate projection including temperature, precipitation, and fire weather index provided by the Center for Climate Resilience and Decision Science (CCRDS) at Argonne National Laboratory. Data is at a resolution of 12 km2.	Link
National water dashboard by USGS	Contains a lot of useful water information based on station data, including streamflow, surface water, ground water levels, water quality, and weather observation and forecast.	Link

Monitoring:

hydrological drought based on streamflow: https://waterwatch.usgs.gov/index.php?id=ww_drought

storm-tide monitoring: https://www.usgs.gov/special-topics/water-science-school/science/storm-tide-monitoring#overview

USGS Water data (can be requested and then downloaded): https://waterdata.usgs.gov/nwis detailed site-level data about stream flow, such as gage height, discharge, both real-time monitoring, historical information, and 7-day forecast is provided. This is the corresponding map viewer: Water watch: https://waterwatch.usgs.gov/index.php.

Map information of atmospheric and hydrologic sites: https://maps.waterdata.usgs.gov/mapper/index.html

Coastal change

Flooding is largely related to hurricane and then related to coastal changes

USGS coastal hazard change portal: https://marine.usgs.gov/coastalchangehazardsportal/

National hurricane center: https://www.nhc.noaa.gov/refresh/graphics_at4+shtml/102341.shtml?cone#contents

USGS Hurricane resources: https://www.usgs.gov/hurricanes

National Weather Service River Observations and Forecast: https://water.weather.gov/ahps/forecasts.php A map viewer, contains information of observations, forecast, and long-range flood outlook, as well as flood hazard warning. soil moisture, stream analysis anomaly, flood inundation.