ALEXANDRIA, VIRGINIA. The U.S. Army Corps of Engineers (USACE) has issued Engineering Technical Letter
ETL 1100-2-2 establishing guidance for the appropriate use of paleoflood analyses and information to support
USACE hydrology and hydraulics (H&H) decision making.
Paleohydrology describes the evidence of the movement of water and sediment in stream channels before the time of continuous hydrologic records or direct measurements. The utility of paleoflood information should be considered with respect to the H&H decision at hand, including both the policy and the technical requirements of that decision.
For situations where paleoflood data is potentially useful to H&H decisions, the resources necessary to conduct the investigation should be weighed against the underlying uncertainties and assumptions. Paleofloods can provide direct and useful information about stage histories and can be used, given caution, to estimate discrete event discharge values. However, there is limited evidence to support using paleoflood information to estimate a series of hydrologic events with multiple peaks, flood volumes or durations.
The ETL provides guidance for the application of paleoflood information to H&H decision making. Information in its appendices includes a summary of the appropriate use of paleoflood information specifically for USACE H&H decision making, examples of paleohydrological studies, methods for calculating paleoflood discharge, and calculation of paleoflood volume.
Will Veatch of USACE New Orleans District (MVN) and Dr. Kate White of the Institute for Water Resources (IWR) prepared the guidance based on the externally peer-reviewed report Appropriate Application of Paleoflood Information for the Hydrology and Hydraulics Decisions of the U.S. Army Corps of Engineers led by Dr. David Raff, formerly USACE, and now with the U.S. Bureau of Reclamation. More information about the report and about the uses of paleoflood information for H&H decision making can be found on the Responses to Climate Change website.
For more information, visit www.iwr.usace.army.mil.