REPORT TITLE:
Stream Gages; DLNR; USGS


DESCRIPTION:
Appropriates funds to the DLNR for the engineering branch of the
land division to partly fund the continued operation and
maintenance of streamflow and crest-stage gaging stations with
the United States Geological Survey, to provide data for
hydraulic and hydrologic flood analyses.  (SD1)

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                                                        2998
THE SENATE                              S.B. NO.           S.D. 1
TWENTIETH LEGISLATURE, 2000                                     
STATE OF HAWAII                                                 
                                                             
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                   A  BILL  FOR  AN  ACT

MAKING AN APPROPRIATION TO PROVIDE DATA FOR HYDRAULIC AND
   HYDROLOGIC FLOOD ANALYSES.



BE IT ENACTED BY THE LEGISLATURE OF THE STATE OF HAWAII:

 1      SECTION 1.  The legislature finds that the United States
 
 2 Geological Survey currently operates ninety-five crest-stage
 
 3 gages as of water year 2000.  The gages provide information on
 
 4 peak flows for the streams upon which they are located.  The
 
 5 Honolulu forecast office of the National Weather service uses the
 
 6 historical record from these gages, in conjunction with other
 
 7 data sources (e.g., continuous record gages, rain gages, etc.),
 
 8 to help determine rainfall-to-runoff relationships for flood
 
 9 prone streams.  These relationships are then used to determine
 
10 thresholds of rainfall for when a particular stream will start to
 
11 experience flash flooding.  For example, if forecasters know that
 
12 a particular stream floods a low-lying residential area with
 
13 5,000 cubic feet per second of discharge, they can use the
 
14 rainfall-runoff relationship to determine how much rain is
 
15 required to produce this magnitude of discharge.  The rainfall-
 
16 to-runoff relationships are stream-specific so it is obviously
 
17 advantageous to have as much stream flow data as possible.  Since
 
18 forecasters cannot realistically have data for every stream, they
 
19 apply the rainfall-to-runoff relationships of instrumented stream
 

 
Page 2                                                     2998
                                     S.B. NO.           S.D. 1
                                                        
                                                        

 
 1 basins to non-instrumented stream basins with similar physical
 
 2 characteristics.
 
 3      Part of the modernization and improvement of the National
 
 4 Weather Service's hydrology program is the use of Doppler radar
 
 5 data processed through the Areal Mean Basin Estimated Rainfall
 
 6 (AMBER) program.  The AMBER program allows forecasters to view
 
 7 basin specific rainfall updated every five to six minutes and
 
 8 provides the rainfall component of a stream-specific rainfall-to-
 
 9 runoff relationship.  When used with the proper flash flood
 
10 threshold, the AMBER program provides an extremely powerful tool
 
11 to help forecasters provide flash flood warnings to the public.
 
12 Accurate flash flood thresholds for use in AMBER require data on
 
13 peak stream flows.  These thresholds can change over time due to
 
14 natural or artificial changes in the stream basin.  Thus, without
 
15 updated peak flow records for calibration, the accuracy of the
 
16 flash flood thresholds will slowly degrade over time.  It follows
 
17 that the elimination of data from the forty-seven crest-stage
 
18 gages supported by the department of land and natural resources
 
19 will have a negative impact on forecasters' ability to provide
 
20 accurate flash flood warnings.  This impact will not be felt
 
21 immediately, but will increase over time.
 
22      As a final point, the elimination of forty-seven crest-stage
 
23 gage sites will also negatively impact forecasters' ability to
 

 
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                                     S.B. NO.           S.D. 1
                                                        
                                                        

 
 1 conduct post-flood analyses.  For the National Weather Service
 
 2 and many other agencies, the lessons learned from post-flood
 
 3 analyses and reports are an important tool in improving warning
 
 4 and flood mitigation services to the public.  Since the loss of
 
 5 forty-seven sites represents a significant reduction in available
 
 6 peak flow data across the State of Hawaii, forecasters will lose
 
 7 their ability to accurately assess the conditions that occur
 
 8 during an actual flood event.
 
 9      SECTION 2.  There is appropriated out of the general
 
10 revenues of the State of Hawaii the sum of $0, or so much thereof
 
11 as may be necessary for fiscal year 2000-2001, for the
 
12 engineering branch of the land division to partly fund the
 
13 continued operation and maintenance of streamflow and crest-stage
 
14 gaging stations with the United States Geological Survey, to
 
15 provide data for hydraulic and hydrologic flood analyses.
 
16      SECTION 3.  The sum appropriated shall be expended by the
 
17 department of land and natural resources for the purposes of this
 
18 Act.
 
19      SECTION 4.  This Act shall take effect on July 1, 2000.