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Appropriate Application of Paleoflood Information for Hydrology and Hydraulics Decisions

ALEXANDRIA, VIRGINIA. The U.S. Army Corps of Engineers (USACE) infrastructure, operations, safety and maintenance programs are facing growing stresses caused by aging infrastructure, hydrologic nonstationarity, urban growth, coastal development, evolving navigation and shipping practices, changing agricultural practices, and increasing recognition of the need for ecosystem restoration.

The Hydrology, Hydraulics, and Coastal (H,H,&C) Community of Practice frequently conducts studies and assessments that require a wide range of currently available data that can be applied to varying scales of economic and technical decisions. Practitioners continually search for additional information that can inform future decisions.

Utilizing paleoflood data for supporting the decisions of USACE hydrology and hydraulics (H&H) practitioners is the subject of a new investigation and report that synthesizes relevant literature and scientific findings related to USACE H&H assessments. Paleohydrology describes the evidence of the movement of water and sediment in stream channels before the time of continuous hydrologic records or direct measurements.

Appropriate Application of Paleoflood Information for the Hydrology and Hydraulics Decisions of the U.S. Army Corps of Engineers (pdf, 2.62 MB) investigates utilization of geologically obtained and hydrologically transformed paleoflood data in both the relatively recent past (50-500 years) to the very distant past (500-10,000 years). It presents reasonable conclusions and recommendations about the use of such data with respect to the decisions faced by the USACE H&H community.

The main conclusions of the report are:

• 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 cautions, 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.
• Paleoflood information is less useful if it is meant to inform a portfolio of projects or compare locations across a wide geographic region that has varied terrain and geological contexts.

Paleoflood information is not relevant for all H&H decisions. For example, if the decision leads to the design or modification of a high hazard dam, then the utility of paleoflood information is minimal, as the current design standard is based on the “Probable Maximum Floods” standard. Paleoflood information is largely site specific. USACE is responsible for many very large facilities that have been altered through time, either by geologic or anthropogenic processes. These facilities are not suitable for paleoflood analysis.

The report was written by David Raff, who is a member of the USACE IWR Climate and Global Change team. It is part of a larger effort to explore processes, methods and guidance for hydrology used in climate change impact assessments and adaptation planning and design.

posted February 28, 2013

 

 

Interagency Report Published on Information Required for Short-Term Water Management Decisions

WASHINGTON, DC. Adapting to future climate change impacts requires capabilities in hydroclimate monitoring, short-term prediction and application of such information to support contemporary water management decisions.

These needs were identified in a report, "Short-Term Water Management Decisions: User Needs for Improved Climate, Weather, and Hydrologic Information," published by the Bureau of Reclamation and the U.S. Army Corps of Engineers with the National Oceanic and Atmospheric Administration. IWR’s Climate and Global Change team contributed to the report.

The report identifies how Federal agencies, along with state, local, tribal and non-governmental organizations and agencies are working together to identify and respond to the needs of water resource managers in the face of a changing climate. The report is broken into four categories: Monitoring Product Needs, Forecasting Product Needs, Understanding and Using Information Products in Water Management, and Information Services Enterprise.

"Climate change is adding to the challenges we face in managing a multitude of issues, including water supply, water quality, flood risk, wastewater, aquatic ecosystems, and energy production," Reclamation Commissioner Michael L. Connor said. "Meeting these challenges requires close collaboration among water resource management agencies, operational information service providers, stakeholders and the scientific community."

"This document describes the short-term needs of the water management community for monitoring and forecast information and tools to support operational decisions," said U.S. Army Corps of Engineers Director of Civil Works Steven L. Stockton. "Large water resources systems with water supply goals have very different needs from smaller systems that primarily service flood control purposes. Because of those differences, having a unified report such as this one communicates not only the national-level water resource needs but the local interactions between the water resource management agencies and the weather, climate and hydrologic service and information providers."

Technical specialists from the Corps of Engineers and the Bureau of Reclamation with NOAA’s National Weather Service prepared the report as part of the Climate Change and Water Working Group. It is the second in a series of reports from the working group.

The first report, "Addressing Climate Change in Long-Term Water Resources Planning and Management," was issued in January 2011.

The Short-Term Water Management Decisions report is available online at www.ccawwg.us.

 

posted February 9, 2013