About this project
Mifflin County's original Flood Insurance Rate Maps (FIRMs) were created in the 1970's and 80's and have since become outdated and inaccurate. The Juniata College students edited the original FIRMs using ArcView GIS 3.2, to match the current topography and hydrologic characteristics.
The students were responsible for editing two different zones, the zone
A and zone AE floodplains. Zone A's are 100-year flood areas, where base
flood elevations (BFEs) and flood hazard factors are not determined. In
refining this zone, the width of the floodplain remained a constant factor.
While the floodplains were adjusted to fit the topography and hydrologic
conditions, the overall width remained the same. A detailed descritpion
of how zone A's were edited can be found here.
Zone AE's are 100-year flood areas that already have base flood elevations
and flood hazard factors associated with them. In these zones, the students
used ArcView to add contour lines to the DFIRMs and refined them according
to the BFEs given on the original FIRMs. A detailed description of how
zone AE's were edited can be found here.
Once the zone A and AE floodplains were edited, the corrections were sent
to a project coordinator for Quality Assurance and Quality Control (QA/QC),
a final check to assure that the new adjustments meet FEMA's standards.
After the work had been through the QA/QC process, ground truthing was
completed. In this process, the students visited the sites of several
problematic areas and used a Trimble (DGPS) unit and a digital camera
to study the area to ensure that the DFIRM alterations were accurate.
The project will soon move into its next phase, which includes the refinement
of the zone A's at the problematic areas in the floodplain. This will
be completed using USGS regression equations and normal depth computations.
Experienced engineers will complete further hydrologic and hydraulic modeling
in the appropriate areas.