The mission of the U.S. Geological Survey (USGS) Water Mission Area is to provide the information and understanding needed for wise management of the Nation's water resources. Inherent in this mission is the responsibility of collecting data that accurately describe the physical, chemical, and biological attributes of water systems. These data are used for environmental and resource assessments by the USGS, other government agencies and scientific organizations, and the general public. Reliable and quality-assured data are essential to the credibility and impartiality of the water-resources appraisals carried out by the USGS. The development and use of guidelines for Measuring Discharge with Acoustic Doppler Current Profilers from a Moving Boat are necessary to achieve consistency in the use of scientific methods and procedures, document the methods and procedures used, and maintain technical expertise in the process. USGS hydrographers and hydrologists can use this manual to ensure that the data collected are of the quality required to fulfill our mission. This 2013 update of Measuring Discharge with Acoustic Doppler Current Profilers from a Moving Boat contains the most current information and guidance regarding acoustic Doppler current profilers (ADCPs) used by the USGS at the time of publication. The following memoranda are considered superseded or duplicated by the policy and procedures in this report and need not be referenced in the future: 2012.01-Processing ADCP Discharge Measurements On-site and Performing ADCP Check Measurements 2011.08-Exposure time for ADCP moving-boat discharge measurements made during steady flow conditions 2009.05-Publication of the Techniques and Methods Report Book 3-Section A22 "Measuring Discharge with Acoustic Doppler Current Profilers from a Moving Boat" and associated policy and guidance for moving boat discharge measurements 2009.02-Release of WinRiver II Software (version 2.04) for Computing Streamflow from Acoustic Doppler Current Profiler Data 2006.04-Availability of the report "Application of the Loop Method for Correcting Acoustic Doppler Current Profiler Discharge Measurements Biased by Sediment Transport" by David S. Mueller and Chad R. Wagner (USGS Scientific Investigations Report 2006-5079) and guidance on the application of the Loop Method 2005.05-Guidance on the use of RD Instruments StreamPro Acoustic Doppler Profiler 2005.04-Release of WinRiver Software version 10.06 for Computing Streamflow from Acoustic Profiler Data 2003.04-Release of WinRiver Software version 10.05 for Computing Streamflow from Acoustic Profiler Data iv 2002.03-Release of WinRiver Software (version 10.03) for Computing Streamflow from Acoustic Profiler Data 2002.01-Configuration of Acoustic Profilers (RD Instruments) for Measurement of Streamflow 2002.02-Policy and Technical Guidance on Discharge Measurements using Acoustic Doppler Current Profilers The development of new and improved ADCPs is ongoing, as are the research and practical field experience with existing and new ADCPs, which li...

Flood inundation maps typically have been used to depict inundated areas for floods having specific exceedance levels. The uncertainty associated with the inundation boundaries is seldom quantified, in part, because all of the sources of uncertainty are not recognized and because data available to quantify uncertainty seldom are available. Sources of uncertainty discussed in this paper include hydrologic data used for hydraulic model development and validation, topographic data, and the hydraulic model. The assumption of steady flow, which typically is made to produce inundation maps, has less of an effect on predicted inundation at lower flows than for higher flows because more time typically is required to inundate areas at high flows than at low flows. Difficulties with establishing reasonable cross sections that do not intersect and that represent water‐surface slopes in tributaries contribute additional uncertainties in the hydraulic modelling. As a result, uncertainty in the flood inundation polygons simulated with a one‐dimensional model increases with distance from the main channel.

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In the late 1800s, John Wesley Powell, second Director of the U.S. Geological Survey (USGS), proposed gaging the flow of rivers and streams in the Western United States to evaluate the potential for irrigation. Around the same time, several cities in the Eastern United States established primitive streamgages to help design water-supply systems. Streamgaging technology has greatly advanced since the 1800s, and USGS hydrographers have made at least one streamflow measurement at more than 37,000 sites throughout the years. Today, the USGS Groundwater and Streamflow Information Program supports the collection and (or) delivery of both streamflow and water-level information for more than 8,500 sites (continuous or partial record) and water-level information alone for more than 1,700 additional sites. The data are served online-most in near realtime-to meet many diverse needs; more than 640 million requests for streamflow information were fulfilled during the 2017 water year (October 1, 2016-September 30, 2017).

The one-dimensional approach is reasonable for a prismatic channel in a relatively narrow floodplain but may not be appropriate for sinuous rivers with several tributaries in broad floodplains. Uncertainty in the flood-inundation polygons increases with distance from the main channel for which water-surface slopes are simulated. Two-dimensional models are increasingly used for simulating floodplain inundation because of the variability in topography across the floodplain, particularly in wide floodplains with numerous tributaries.