Agricultural Flood Damage – The agricultural economic loss resulting from a flood event, including the investment cost to bring a crop to market and net revenue (income minus harvest costs).

 

Arrival Time Grid – A grid that specifies when water reaches a predefined threshold at each cell. For a typical loss of life assessment, default arrival time threshold is two feet. For an agricultural damage assessment, the arrival time threshold will typically be when the cell gets wet, which would be described as an arrival of anything greater than zero feet of water.

 

Capital – This generally refers to the produced durable goods that can be used in the production of goods and services. In HEC-FIA, the value of structures and the value of their contents are used as a proxy for the capital in an area.


Capital Loss – The reduction in available capital of a region from some sort of shock to the economy of a region.

 

Chance Zone – Flood lethality zone with conditions in which people have no shelter from the flood, and have a chance of being rescued or finding floating debris while drifting (refer to the references in Section A.3).

 

Cleanup Period Duration – The amount of time necessary to clean the damages caused by a flood.

 

Common Computation Point – A location along a stream alignment where time-series information is exchanged between models. In HEC-FIA, common computation points (CCPs) are the locations of the hydrographs, stage-damage (or discharge) relationships, flood or drought impacts, and emergency response information that was developed for an impact area.

 

Compromised Zone – Flood lethality zone with conditions in which shelters have been severely damaged by the flood, increasing the exposure of flood victims to violent floodwaters (refer to the references in Section A.3).

 

Continuous Distribution – For any given probability between zero and one, a continuous distribution is a function that produces a result that is continuous and is a real number.

 

Convergence Confidence Interval – As sample size increases, the value of the running mean of the results of the Monte Carlo sample should approach the expected value. The user-specified confidence interval gives the user indirect control of how many iterations to run, based on how likely it is that the result and the full distribution of the sample is within the user's specified level of confidence.


Convergence Tolerance – Used to specify when the rate of change in the computed confidence interval has reached the specified level of stability to satisfy the convergence criteria for the simulation. When the tolerance is met on the confidence interval, the simulation stops iterating.

 

Crop Loss Relationship – Defines the percentage of crop loss based on the number of hours (i.e., duration) crops are inundated each month.

 

Cross Section – A one-dimensional line defined perpendicular to the streamflow defining the X-Y coordinate points along that line.

 

Depth – For HEC-FIA flood damage analyses, depth is the difference between the water surface elevation at a damageable asset and a critical elevation (some threshold or the ground).

 

Depth-Percent Damage Relationship – Defines the percent damage caused to a structure, a structure's contents, and any vehicles stored at a structure at incremental depths.

 

Digital Elevation Model (DEM) – A representation of continuous elevation values over a topographic surface by a regular array of z-values (elevations), referenced to a common datum (refer to the references in Section A.3).

 

Duration – The length of time an area is inundated. In HEC-FIA, duration is defined as the total amount of time between the first time the floodwater depth exceeds the threshold depth (zero feet for agricultural damage calculations and two feet for ECAM calculations) and the last time the floodwater depth exceeds the threshold depth.

 

Duration Grid – A grid that specifies the duration of inundation for each cell.

 

Economic Consequences Assessment Model (ECAM) – A computable general equilibrium model with separate datasets for each county in the United States used to compute indirect economic impacts.

 

Elevation – A vertical distance compared to a selected vertical datum. In this document, the terms "stage" and "elevation" are used interchangeably. Stage and elevation should not be confused with depth, which is the stage/elevation less a local datum such as the ground surface elevation or a structure's first floor elevation.

 

Evacuation – The movement of people from a hazardous area to a safe location.

 

Evacuation Outcome Category – One of three categories to which people are assigned by HEC-FIA depending upon where they are when the flood wave arrives. These categories include cleared (people who evacuate safely), caught (people who are caught evacuating), or not mobilized (people who remain in structures).

 

Evacuation Point – The point on the hazard boundary that is determined by drawing a straight line from a structure perpendicular to the hazard boundary.


First Planting Date – The first date that a crop can be planted to reach a full yield.

 

Fixed Crop Planting Cost – The unchanging monetary cost of planting an agricultural crop. Usually, this would represent rent or land payments.

 

FLO-2D – A model used to route floods in two dimensions through the simulation of channel flow, unconfined overland flow, and street flow over complex topography.

 

Flood Duration – The length of time from the beginning to the end of a flood event.

 

Flood Lethality Zone – See Lethality Zone.

 

Georeferenced – A feature that is spatially referenced to a particular location with a known geographic coordinate system.

 

Harvest Cost – The monetary cost of conducting gathering, picking, and hauling operations to get a crop to market.

 

Harvest Date – The date on which the harvest of a crop occurs.

 

Hazard Area Boundary – The border for the area where flood depths are equal to or greater than the user-defined depth of flow resulting in dangerous conditions.

 

HAZUS Database – A national geodatabase containing consistent data (for example, demographics, structural inventories, essential facilities, and public utilities) for every state, county, census tract, and census block. HEC-FIA can import portions of this database for rapid assessments or reconnaissance level studies.

 

HEC – HEC (Hydrologic Engineering Center) is an organization within the Institute for Water Resources (IWR), which is the designated Center of Expertise for USACE in the technical areas of surface and groundwater hydrology, river hydraulics and sediment transport, hydrologic statistics and risk analysis, reservoir system analysis, planning analysis, real-time water control management, and a number of other closely associated technical subjects.

 

HEC-DSS – HEC Data Storage System, a database system that stores time-series and paired data for inventory, retrieval, and archiving for water resource applications.

 

HEC-FIA – HEC Flood Impact Analysis, a USACE software application, is a tool for quantifying the consequences of flood events that provides the capability of estimating the impacts, damage, loss of life associated with flood events, and the benefits attributed to flood risk management projects.

 

HEC-HMS – HEC's Hydrologic Modeling System, a USACE software application that is designed to simulate the complete hydrologic processes of dendritic watershed systems.


Holdout - A reservoir holdout is simply a flow time series of what the given reservoir “held out” or stored during the event. Within HEC-FIA, "holdout" is used to define inundation configurations (Holdout - Cross Section and Holdout - Grids) where the user defines the flow time series holdout for a specified reservoir. These two inundation configurations are most often used in Flood Damages Reduced calculations.


HEC-LifeSim – HEC-LifeSim, a USACE agent-based software application that estimates life loss with the fundamental intent to simulate population redistribution during an evacuation. This application requires detailed consideration of these factors: the flood event, the number of people exposed to the flood event, and the loss of life among the threatened population.

 

HEC-RAS – HEC's River Analysis System, a USACE software application that conducts one and two dimensional hydraulic calculations for a full network of natural and constructed channels.

 

HEC-RAS Mapper – HEC's River Analysis System interface included in HEC-RAS beginning with Version 4.1, which allows for the use and visualization of floodplain geospatial data, along with HEC-RAS simulation results, within a single modeling environment.

 

HEC-ResSim – HEC's Reservoir System Simulation, a USACE software application used to model reservoir operations.


Hydraulic Characteristic – A trait that is used to describe one attribute of a flood event, such as depth, arrival time, or flood duration.

 

Indirect Loss – Losses resulting from reductions of capital and labor for a region. Indirect losses are characterized as the change in production of the economy due to a change in the market equilibrium.

 

Initial Seed – A value entered into the random number generator to create a uniformly distributed pseudorandom number sequence as part of a Monte Carlo simulation.

 

Inundation Data – Information that is used to describe a flood event based on input from grids, cross sections, storage areas, and common computation points.

 

Labor – The portion of the population involved in providing goods and services to the economy.

 

Labor Loss – A reduction in available labor due to some shock to the economy. This could be due to inability to report to work, or due to evacuations from the floodplain for safety.

 

Last Planting Date – The latest date that a crop can be planted, but with a reduction in yield.

 

Lethality Rate – A relationship between number of deaths and water depth used in HEC-FIA to define potential loss of life for the lethality zones.

 

Lethality Zone – Categorization of physical flood environments based on the available shelter and local flood depths and velocities.  HEC-FIA assigns people to one of three zones (safe, compromised, or chance), depending upon their evacuation outcome categories. 

 

Log Normal Distribution – A distribution used to parameterize random variables that are always greater than zero.

 

MIKE 21 – A two-dimensional hydraulic modeling software program developed and maintained by DHI.

 

Mobilization Relationship – Describes how quickly the population mobilizes given they have received and understood a warning.

 

Model – A mathematical representation of a system that relates something unknown (the output) to something known (the input). For HEC-FIA, the inputs include hydrologic/hydraulic data, watershed data, economics data, and various global data; outputs include various estimated flood impacts and loss of life and project benefits.

 

Monte Carlo Simulation – A mathematical model used to describe the relationship of the input variables to the output variable of interest. Each input parameter is expressed as a continuous distribution and a randomly drawn number can be obtained for each parameter. The mathematical model then calculates a sample from the randomly described set of input variables. This process is repeated to provide a set of deterministic results each from a different set of input parameters. The result is then a distribution of possible outcomes based on the model, from which the central tendency can be evaluated.

 

Non-evacuation Depth – Depth at which it becomes unsafe to evacuate.  The default non-evacuation depth in HEC-FIA is two feet, based on the assumption that most vehicles float will float at a depth of two feet.

 

Normal Distribution – Data is described by this distribution using a mean and standard deviation, with the mean serving as the maximum result that can be achieved in the result space. The value range is always negative infinity to positive infinity.

 

Population At Risk (PAR) – The number and location of people within the potentially inundated area during day and night conditions exposed to the flood hazard. PAR includes people permanently residing in the inundated area (and accounting for commute patterns), as well as temporary residents.

 

Population Impacted – The number of people within structures that get wet from a flood event.

 

Probability Density Function – Represents the instantaneous relative change of the cumulative distribution, which is beneficial in displaying the relative likelihood of a parameter to take on a particular value within a range.

 

Reconstruction Period Duration – The amount of time necessary to repair structures and/or construct replacement structures after a flood event.

 

Safe Zone – Flood lethality zone with conditions in which people are either dry or exposed to relatively quiescent floodwater or shallow flooding unlikely to sweep people of their feet (refer to the references in Section A.3).

 

Shapefile – A vector data storage format for storing the location, shape, and attributes of geographic features. A shapefile is stored in a set of related files and contains one feature class (refer to the references in Section A.3).

 

Simplified LIFESim – A simulation method that estimates the loss of life resulting from a dam failure based upon HEC-LifeSim concepts and methods, but with reduced data requirements. Simplified LIFESim is used within HEC-FIA.

 

Stream Alignment – A geographic representation of a stream system in a watershed. The alignment indicates where junctions occur and provides a sense of distance and scale. In HEC-FIA, stream alignments are composed of stream elements.

 

Stream Station – A station along a stream normally denoted as miles above the mouth of a stream.

 

Structure – A building or infrastructure facility that may be analyzed during flood events.

 

Structure Inventory – A geospatial record of the attributes of unique structures relevant to flood impact analysis. Structure inventory data is used to compute an estimate of consequences at the individual structure, occupancy type, damage category, and impact area.

 

Terrain Model – A terrain model is a Digital Elevation Model that represents the ground elevation for the region being studied in a grid cell by grid cell format.

 

Triangular Distribution – Data is described by this distribution using a minimum, maximum, and mode value, with the mode serving as the maximum result that can be achieved in the result space.

 

Uniform Distribution – Data described by this distribution are uniformly spread between the minimum and maximum values that can be achieved in the result space. Every value outside of the minimum and maximum values results in a zero.

 

Unit Price – The monetary cost of each unit of an agricultural crop.

 

Variable Crop Planting Cost – The monetary cost of planting an agricultural crop based on the timing of when the planting occurs.

 

Water Surface Elevation – Stage referenced to a particular elevation datum.

 

Yield – The amount of crop produced per unit area.