Federal Guidelines for Dam Safety: Selecting and Accommodating Inflow Design Floods for Dams

Versions: 1986, 1985, 1984

The main objectives of these guidelines are to recommend appropriate procedures for selecting and
accommodating the Inflow Design Flood based on current and accepted practices and to promote a
reasonable degree of consistency and uniformity among state and federal agencies. Appropriate
selection of the Inflow Design Flood is the first step in evaluating and designing a dam to address
hydrologic potential failure modes and reduce risks to the public.
Existing guidelines of most state and federal agencies for evaluating the hydrologic safety of dams
were written in the late 1970s. Since that time, significant technological and analytical advances
have led to better watershed and rainfall information, improvements in the analysis of extreme
floods, greater sophistication in means to quantify incremental dam failure consequences, and tools
for evaluating hydrologic events in a risk-based context. Lead agencies and professionals in the
nation’s dam safety community recognize the need for updated guidelines for evaluating the
hydrologic safety of dams and, in particular, for selecting an appropriate Inflow Design Flood.
This document is intended to provide a flexible framework within which both federal and state
agencies can develop and update guidelines according to their varied goals and resources. The
guidelines herein are not intended to be a mandate for uniformity nor provide a complete manual of
all procedures available for estimating or accommodating Inflow Design Floods. The basic
philosophy and principles are described in sufficient detail to promote common and/or compatible
approaches among state and federal agencies in the design and evaluation of dams from the
standpoint of hydrologic safety.