Hydrologic Hazards Science at the U.S. Geological Survey (1999) / Chapter Skim
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3 Data Collection, Techniques Development, and Research
3 Data Collection, Techniques Development, and Research
Pages 23-33
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From page 23... ...
performs critical functions in relation to hydrologic hazards and extreme hydrologic events (see Figure 3.1~. These functions encompass broad areas of data collection, techniques development, and research.
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From page 24... ...
FLOODS Floods are the most visible and immediately destructive extreme hydrologic events. Floods create hazards in several ways: · loss of life, property, and services and other social impacts associated with flood flows; · scour and deposition in natural channels, including scour around bridge piers and other structures located in the floodway; · erosion of channel banks and beds and deposition of sediments in channels, impoundments, and other areas; .
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From page 25... ...
During floods, destruction of natural habitat occurs through channel erosion and excessive sediment deposition, typically exacerbated by increased peak flood flows associated with urbanization and by increased erosion associated with some agricultural practices, water management, construction activities, and other earth-moving operations. Adverse water quality conditions can result from stormwater runoff, both within and downstream of urban, agricultural, silvicultural, and mining areas.
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From page 26... ...
The definition of regions based on hydrologically related similarity criteria may offer improvements in terms of reduced standard errors (Tasker et al., 1996~. Such regional definitions related to the hydrologic responses of watersheds should be continued and expanded to include hydrologic characteristics such as climatic variables and soil and geologic variables in addition to the commonly used physical characteristics of watersheds.
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From page 27... ...
that are used only rarely, yet collection of data during extreme events is critical to improved understanding, prediction, and warnings. It may be appropriate for the USGS to evaluate the role of peak stage recorders as part of an alternative data collection paradigm of collecting slightly less accurate information at more geographic sites.
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From page 28... ...
If a key stream gage becomes inoperative during a major flood event, a flood warning system could be rendered ineffective, resulting in more damages and losses than might have occurred using older technologies. Research Needs Related to Floods Data on relatively frequent peak flows are naturally far more readily available than data on extreme events, which by definition occur infrequently and likely are not represented in commonly available records of length.
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From page 29... ...
Continued research is needed to develop and improve techniques for extrapolation of hydrologic data and predictions to extreme events. The use of stochastically generated rainfall events implicitly relies on the same assumption inherent in statistical flood frequency analysis that extreme rainfalls follow the same statistical patterns as the more frequent rainfalls that are the basis for estimating the parameters of stochastic models.
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From page 30... ...
The period chosen will directly impact the data's sample sizes, which will impact the number and type of drought events. For a given hydrologic record, a shorter averaging period results in a larger number of drought events, while a longer averaging period results in a smaller number of drought events.
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From page 31... ...
Prolonged droughts occur when largescale anomalies, such as those associated with ENSO, in atmospheric circulation patterns persist for months, seasons, or years (NDMC, 1995, 1997~. Hydroclimatological features, which describe the spatial and temporal connections between atmospheric circulations and the hydrological cycle at the regional scale, can be used to assess the predictability of drought severity and duration.
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From page 32... ...
Monitoring of ground water levels and soil moisture also is extremely important during drought periods, and long-term fluctuations in ground water levels are often an excellent indicator of overall climatic patterns. These measurements need to be combined with climatological measurements of precipitation, temperature, wind, soil moisture, and other parameters in order to create a complete picture of droughts as extreme hydrologic events.
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From page 33... ...
Improved data collection can result from advances in instrumentation for low-flow measurement and soil moisture measurement at remote sites to acquire a regional perspective. Better ability to predict drought periods could be applied to improve water management systems, enabling better planning by water users (e.g., municipalities and agriculture)
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