Each year, USACE districts and divisions are required to report AFDR totals for all applicable projects within their boundaries to USACE Headquarters. These data are entered into a national database, and the resulting figures are consolidated into a comprehensive report and submitted to Congress as Appendix G of the Annual Report on Civil Works Activities.

Since 2013, districts have reported FDR data by individual project, providing greater granularity and accountability. Moving forward, this information is expected to play an increasingly important role in USACE budget planning and resource allocation.

Legacy Methods and Their Limitations

Historically, districts have used a variety of approaches to calculate AFDR, with many relying on a legacy method based on aggregated stage-damage curves. This approach typically divides the watershed into broad reaches and associates damages with a single curve at a key river gage. While these curves are adjusted for inflation, they often do not reflect current floodplain conditions or infrastructure, many of which have changed significantly since the curves were created. As a result, AFDR estimates using this method may be outdated or underestimated.

In addition, legacy workflows often depend on command-line tools and numerous spreadsheet-based calculations, which can be time-consuming, error-prone, and difficult to maintain or audit over time.

A Modern Approach Using CWMS

This guide introduces a modernized, geospatially-informed methodology for calculating AFDR using CWMS models developed under the CWMS National Implementation Plan (NIP). By integrating hydrologic, hydraulic, and reservoir simulation modeling with geospatial data on structure and agricultural inventories, districts can generate more accurate, detailed, and transparent AFDR estimates.

This approach not only improves technical accuracy, but also enables districts to visualize where, how, and why flood damages are being reduced—supporting better communication with stakeholders and more informed decision-making.

Annual Report to Congress

In accordance with the Rivers and Harbors Act of 1888 (Section 8, Sec. 1812, Revised Statutes, 40 U.S.C. §50) and the Water Resources Development Act of 1986 (Public Law 99-662, Section 925(b)), the Assistant Secretary of the Army for Civil Works submits an annual report to Congress detailing USACE Civil Works activities.

This report follows guidance outlined in Engineer Regulation (ER) 25-2-1, which defines the timeline and procedures for report preparation. The report is delivered in two volumes:

  • Volume I provides summaries, key accomplishments, and highlights of Civil Works programs.
  • Volume II includes detailed project-level data, including Appendix G: Flood Damages Suffered and Prevented.

Appendix G compares actual operations of Corps-managed infrastructure to hypothetical “without-project” scenarios to quantify flood damages prevented. It also incorporates data on flood damages suffered and lives lost, primarily sourced from the National Weather Service (NWS) and the National Oceanic and Atmospheric Administration (NOAA), supplemented by historical USACE data.

Past versions of Appendix G are available on the Hydrology, Hydraulics, and Coastal (HH&C) Community of Practice (CoP) Knowledge Management site for reference.