|
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />I
<br />
<br />4.0 Methods
<br />
<br />4.1 DoJa Collection and Field Work
<br />
<br />The first step in delineating a floodplain is to collect as much existing data as possible, The
<br />original field expedition was made on June 3rd and 4th, 2002, On this trip Tom Browning, Tom
<br />Gilman, and Gared Grube traveled to Delta County to meet with community officials for Delta
<br />County and Orchard City and to collect necessary field data. The officials included Duane
<br />Freeman, the Emergency Preparedness Coordinator for Delta County, and Jerry Doss and Jim
<br />Erickson, the town administrator and mayor, respectively, of Orchard City, These officials were
<br />able to provide the floodplain history including past over bank flow problems and significant
<br />flood events, an important first step in assessing the likely extent of the inundation during a
<br />flood, as well as currently existing data, Other historical data were obtained through archived
<br />documentation of historical problems due to past flooding from designated city files, the CWCB,
<br />the USGS, past press releases, and other sources as they were found,
<br />
<br />In addition, all of the necessary information that was not currently available from previous
<br />documentation was obtained from field observations and measurements, Measured dimensions
<br />and an inventory of all drainage structures, including bridges and culverts, were obtained, All of
<br />the field observations and the objects being measured were photographed, In addition, the
<br />channel and bankfull (the extent of the channel that can contain the maximum amount of water
<br />without inundating of the floodplain, usually accommodating the flow that occurs every 1,5
<br />years) of the basin were photographed for a visual reference of the watershed, These bridges,
<br />culverts, and bankfull positions were later entered into HEC-RAS for the hydraulic analysis, The
<br />data can be viewed by opening the HEC-RAS files contained on the attached CD, Appendix F
<br />gives a description of the information obtained on the disk.
<br />
<br />In addition to obtaining the history and inventorying the drainage structures, existing GIS data
<br />was obtained, GIS data can be found from city, county, state, or federal agency GIS departments,
<br />At a minimum, GIS data should include natural contours with hills, depressions, valley, and
<br />mountain elevations and slopes; hydrologic features with streams, rivers, ponds, lakes,
<br />
<br />10
<br />
|