Basics of Modeling Floods: Tools and Data to Assess Risk of Flooding in Florida

Models of floods incorporate data on changing risk into planning for resilience 

Communities across Florida experience flooding from a variety of sources, and this risk is increasing. Sources of concern include sea level rise, extreme rainfall, tides, storm surge, and groundwater rising above the land’s surface. Due to Florida’s geography, terrain, and geology, two or more of these hazards can occur at the same time, resulting in increased risk of flooding and combinations of relatively rare events that are challenging to predict.    

One tool used by practitioners to meet the challenge of assessing risk are models: simulations of the real-world environment used to investigate different scenarios related to flooding. By simulating hazards under future conditions, models allow engineers, planners, and decision makers to estimate potential risks and take action to protect vulnerable assets. 

What is risk?  

Risk is the likelihood that a hazard will cause specific consequences. It accounts for the magnitude of the hazard, probability that the hazard will occur, and the vulnerability of a system, community, or asset. In Florida, factors such as lakes and rivers, groundwater, an extensive coastline, and a relatively wet climate contribute to a high risk of flooding for many communities.  

 Models of floods can simulate risks under anticipated conditions. In other words, they illuminate the exposure of assets or communities to changes in hazards. When paired with information about vulnerability, data from models can clarify changing risk and guide mitigation.  

Why is the risk of flooding changing?  

Flooding in Florida is changing. Increasingly extreme rainfall, sea level rise, and aging infrastructure all contribute to more frequent and intense flooding.  

The likelihood and magnitude of hazards has been typically evaluated by characterizing past events, but this approach assumes that historical observations are a reliable predictor of future risk. This assumption is becoming less dependable because key drivers of flooding are changing more rapidly than they have in the past. Dynamic circulation models, which capture the global physical processes that drive hazards associated with flooding, produce estimates of future conditions. Results from these models can be used to define scenarios for testing in more localized modeling of flooding.  

Basics for modeling flooding 

Models simulate processes that operate in the real-world to predict the behavior of floodwaters and estimate variables such as depth, velocity, and extent of flooding. They can assess changes in the risk of flooding from different hazards under current and future climatic conditions, allowing practitioners to plan and prepare for emergencies before they happen. 

What needs to be considered for modeling?  

All flood models require data on the natural environment to best simulate the real world. Required characteristics include where, when, and how much water is moving into and through an area. The type of data and level of detail needed depend on the question being addressed and the availability of data. 

Generally, there are two types of data required to model floods. Environmental data are used to establish conditions in the area being analyzed. They can include topography (elevation), weather, hydrology (flows of water), and land use. Physical principles are integrated into models through equations that represent the movement of water.  

What types of models can be used to investigate flooding? 

Depending on the area, scope, and purpose of the project, different types of models may be utilized to simulate flooding. There are four common types of models:  

Hydrologic & hydraulic (“H&H”) models are used to simulate pluvial (rainfall) or fluvial (riverine) flooding. These models estimate the amount of water (hydrology) as well as its extent and spread (hydraulics).  

Coastal (hydrodynamic) models simulate tides, waves, wind-driven currents, and water levels. They are often used to estimate impacts of coastal storms through storm surge and changes in the height of tides. 

Groundwater models simulate changes in water tables and water movement below the ground. They require geologic, topographic, and meteorological data.  

Compound flooding or comprehensive models simulate the interaction of two or more flood events that result in greater flooding than would have occurred from a single hazard. For example, storm surge combined with heavy rain, which leads to more inundation in a coastal area than typically caused by either factor.  

Different drivers of flooding that can be simulated by models.

Applications of models of flooding

A model can have a range of outputs that focus on the probability and magnitude of flooding, such as flood depth, velocity, and extent. Similar to the inputs, the outputs of a model are heavily dependent on the type of flooding being simulated.  As shown in the graphic below, models of flooding are applied in numerous ways by government agencies, insurers, banks, engineering and planning firms, emergency responders, and financial investors. Among other things, models of flooding can guide investment of limited resources, evaluate risk to inform decisions about insurance, and guide design of drainage.  

Examples of how models of flooding are used by practitioners.  

Florida’s Statewide Flood Model Inventory  

Some of the modeling completed for Florida has begun to be documented in the Florida Statewide Flood Model Inventory. The inventory was initiated in December 2023 by the Florida Silver Jackets, with the goal of cataloging models of floods at the basin-level (HUC-8, HUC-10, HUC-12). The inventory contains descriptive information for existing models of flooding, but it does not contain inputs, code, or outputs. The inventory enhances the capacity of local communities as they investigate risks of flooding, reduces duplicative efforts, mitigates loss of institutional knowledge, identifies models or datasets that can be reused or refined, and highlights gaps or areas in need of modeling.  

Simulating hazards for planning resilience 

Models of flooding are useful simulations for evaluating the way different hazards affect an area of interest. They are used for a variety of purposes, but in all instances, they can help characterize Florida’s changing risk of flooding.  

Visit the Florida Statewide Flood Model Inventory to explore the metadata available on existing models of flooding across the state. For more on how the Florida Flood Hub supports modeling, see the previous blog “Climate and Flood Models Illuminate Changes to Florida’s Risk of Flooding”.