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Techniques to Evaluate the Modifier Process of National Weather Service Flood Forecasts

Zhu, Zhipeng
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613752950288287

Abstract Details

2020, MS, University of Cincinnati, Engineering and Applied Science: Environmental Engineering.
The operational hydrologists of the United States’ National Weather Service (NWS) develop river forecasts as guidance for those at risk of flood damage and update those flood forecasts in real-time as more information becomes available. They rely on experience and intuition to adjust the inputs, state variables, and parameters of hydrologic models. NWS hydrologists use the term “modifiers” to refer collectively to these adjustments. This paper demonstrates the development and application of tools (statistical and graphical) to aid operational hydrologists in the achievement of accurate flood forecasts. Analysis of variance (ANOVA) identifies the relative contribution to forecast uncertainty of each modifier. Heat map visualizations illustrate the lead-time, and season-specific effects of their modifiers choices. The tools provide operational hydrologists with insight into which of three commonly applied modifiers (precipitation, soil moisture, and unit hydrograph shape) are most likely to provide improvement in flood forecast accuracy. The tools are demonstrated for a case study of four watersheds within in the Ohio River Valley, using data for flood events sampled from 1990 to 2018. The findings of this research show that operational hydrologists in the Ohio River Basin would do well by applying no modifiers in the winter (leaving hydrologic input variables and parameters at baseline values). While the forecast might be improved by real-time adjustments to the unit hydrograph in summer months, recommendations for particular unit hydrograph modification levels cannot be made with confidence. These findings call into question the modifier adjustment program as a standard process. In the evaluated cases, modifiers do not systematically improve flood forecasts. It was determined that forecasts could be improved by better calibration of hydrologic models or techniques for reduction of precipitation uncertainty.
Patrick Ray, Ph.D. (Committee Chair)
Xi Chen, Ph.D. (Committee Member)
Drew McAvoy, Ph.D. (Committee Member)
60 p.
Environmental Engineering
National Weather Service; Flood forecast; Ohio River Basin; Operational hydrology

Recommended Citations

Citations

  • Zhu, Z. (2020). Techniques to Evaluate the Modifier Process of National Weather Service Flood Forecasts [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613752950288287

    APA Style (7th edition)

  • Zhu, Zhipeng. Techniques to Evaluate the Modifier Process of National Weather Service Flood Forecasts. 2020. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613752950288287.

    MLA Style (8th edition)

  • Zhu, Zhipeng. "Techniques to Evaluate the Modifier Process of National Weather Service Flood Forecasts." Master's thesis, University of Cincinnati, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613752950288287

    Chicago Manual of Style (17th edition)

ucin1613752950288287
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This open access ETD is published by University of Cincinnati and OhioLINK.