FLOOD10391 ‎(2)‎

• County: Boulder
• Community: Boulder
• Stream Name: South Boulder Creek
• Title: Proposal, South Boulder Creek Floodplain Study Hydrology and Hydraulic Analyses, RFP No 17-2003
• Date: 3/14/2003
• Prepared For: Boulder Department of Public Works Utilities Division
• Prepared By: Ayres Associates
• Floodplain - Doc Type: Floodplain Report/Masterplan

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AYRES

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Watershed Hydrologic Modeling and GIS

Several GIS software tools have been used extensively to support a variety of
watershed studies and modeling. We are experienced ArcView users and have been
migrating to the ArcGIS platform over the past year. Spatial Analyst, an extension
used with both ArcView and ArcGIS, is used for DEM processing and numerous types
of raster based surface analyses and map calculations. In conjunction with ArcView,
we! use a number of watershed delineator extensions to assist with hydrologic analysis
and modeling. These delineator extensions include tools available within the EPA's
BASINS model and the Hydrologic Modeling and Watershed Delineator extensions
provided by ESRI. Also to supply geospatial information for HEC-RAS and HEC-HMS
applications we can utilize HEC GeoRAS and HEC GeoHMS to maintain a GIS based
approach for data development.

ArcHydro is the latest addition to our water resources GIS capabilities. ArcHydro is an
ArcGIS data model for water resources. The ArcHydro framework provides a data
structure for storing geospatial data describing a water resource system. This
framework can then support a range of water resource models and studies as defined
by project requirements. In addition ArcHydro includes built-in tools for delineation,
hydrologic calculations, and raster analysis.

Project experience in the area of GIS based hydrological analysis and data
development includes basins ranging in size from 10 to 1200 square miles. We are
proficient at obtaining and integrating geographic data from numerous sources into a
cohesive hydrologic information system. This includes preprocessing DEMs of varying
resolution and creating geodata as needed. Specific project tasks for which we have
used our GIS skills include:

A water yield analysis to estimate model flows at a potential diversion point on
the Navajo River for the Jicarilla Apache Tribe of New Mexico. ArcView
watershed delineation was used to calculate the basin parameters necessary to
examine the relationship between basin elevation and water yield.

Delineating several watersheds in support of HEC-RAS modeling for the
Montana Department of Transportation.

Groundwater modeling for the Santa Ana Pueblo located in New Mexico.
ArcView was used to develop and revise input data for a MODFLOW model, to
examine model results, and present those results visually to non-engineers. A
number of custom applications in VB and Avenue were developed for this
project.

Watershed delineation of the Yampa River Basin including preprocessing of
geographic data to create a basin model input file for HEC-HMS.

H~,drology - Flood Frequency

We believe that oftentimes the best information on flood peak frequency is recorded
flows information and as such we will perform a complete statistical evaluation and
probability analysis of the Eldorado Springs gage. We are aware that significant

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