Overview

The HEC-FIA Technical Reference Manual defines the methods, internal algorithms and computations of the HEC-FIA software. A strong understanding of these internal processes will increase the user's ability to identify model limitations, provide suitable inputs, communicate the importance of results, and help validate decisions that HEC-FIA supports. This manual, in conjunction with the HEC-FIA User's Manual, will help users apply the full capabilities of HEC-FIA. The development history, purpose statement, and features of HEC-FIA are documented in the HEC-FIA User's Manual.

Organization

This manual is organized based on the computational procedures of HEC-FIA; each chapter highlights a particular computational process. Information on a specific topic can be found by going directly to the related chapter. However, since all damage computations rely on how hydraulic information is interpreted at a point location in the study area, it is highly recommended that Hydraulic Event Computations be reviewed before any of the subsequent chapters.

Hydraulic Event Computations: This chapter describes how HEC-FIA takes various hydraulic inputs and converts them into summary information at point locations in the floodplain. The conversion processes for four hydraulic input options are described: 1) cross sections; 2) grids; 3) a combination of grids and cross sections; and, 4) prescribed common computation points.

Direct Damage Computations: This chapter describes how HEC-FIA computes direct economic damage using defined depth-percent damage relationships and hydraulic inputs. The inputs, computational steps, and outputs of the direct damage computational routine are described.

Life Loss Computations: This chapter describes how HEC-FIA calculates life loss at a structure. The life loss computations also includes a method to calculate life loss occurring during evacuation.

Indirect Loss Computations: This chapter describes how HEC-FIA summarizes indirect impacts on a county-by-county basis, and divides the indirect impacts by the total available workforce and capital for each county to determine inputs to the Economic Consequences Assessment Model (ECAM). This chapter also describes and provides reference material for the ECAM calculations.

Agricultural Area Damage Computations: This chapter describes how HEC-FIA computes agricultural damage by location due to a hydraulic event.

Population Distributions: This chapter describes how HEC-FIA distributes population from a census database over an existing structure inventory. The population is distributed based on time of day, occupant age, and occupancy type.

Monte Carlo Simulation Computations: This chapter describes how HEC-FIA uses the various inputs to evaluate the uncertainty of a result for a deterministic hydraulic event.

Appendix A, References: This appendix provides a list of USACE guidance, software documentation, online references, and other references.

Appendix B, Glossary: This appendix provides definitions in regards to terms that are used throughout this document.