Ralph
Cheng described how streamgaging data are used for resource appraisal
and allocation, design of water infrastructure, flood hazard planning,
and flood forecasting. A large percentage of the over 7000 gaging
stations operated by the USGS posts river discharge on WWW at near
real-time. However, the river discharge is not directly measured;
rather it is derived from a stage-discharge relation. There is a need
to improve streamgaging technologies to allow river discharge measured
directly at near real-time for delivery to users. Systematic research
and development efforts at the USGS have shown that it is possible
to determine river discharge using non-contact radar systems. The
present state-of-the-technology allows reliable measurement of river
surface velocity from a riverbank, but the channel cross-section must
be determined using ground-penetrating radar (GPR) with the radar
beam pointing normal to river water surface. The USGS plans to continue
this pursuit with the emphasis on a better understanding of the river
hydraulics. The advances achieved from bank-side mounted radar system
for river discharge leads to the concept of an air-borne radar system
that measures river discharge from a helicopter. The helicopter system
is suitable for emergency responses in regional floods and for applications
to regions that are difficult to gain access.
Cheng also described how, as part
of an urban geologic and hydrologic natural hazards initiative,
the USGS attempts to build a near-real time flood simulation and
warning system to complement streamgaging in flood prone river basins.
The proposed system consists of the integration of an atmospheric
forecast model, a regional hydrologic model that sets the appropriate
boundary conditions for a hydraulic model to simulate normal and
flooding river conditions. The unstructured grid UnTRIM model has
been shown to be robust and efficient for simulating flood inundation
in urban areas. Models in the integrated system will be running
concurrently and interactively. When this system is successfully
built and proven valid, the system will be used for flood forecast
and for issuing flood warning at near real-time via the internet.
In summary, the USGS is attempting to advance technologies in streamgaging,
flood hazard studies, and flood warning
for near real-time operations.
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Masayuki
Oote reviewed PWRI's research into hydrologic observations of flood
flows using floats, as well as PWRI's interests in new observation
technologies to replace the present float observation (or to compensate
for the disadvantages of float measurements). PWRI is doing field
research on the influence of bridge pier disturbance on flood flow
measurement; 3-dimential structure of parallel spiral flow and its
impact on the use of floats; and conversion factors to obtain vertically-averaged
velocity by using non-contact surface velocity measurement methods,
pressure-type Flood Current Meter, and ADCP. |