FEMA DFIRM Standards : Hurricane Ike : Bexar County : TxDOT
Grounds Anderson, LLC has assisted FEMA in the development of DFIRM standards, assisted the Harris County Flood Control District in enhancing their geodatabase, performed forensics with historic aerial photography to determine the location and condition of structures, assisted in the preparation of a countywide impervious cover mapping in Bexar County, Texas, pioneered the use of LiDAR in Special Flood Hazard Area and Inundation Mapping in the Texas Gulf Coast, and tracked changes in a developing subdivision.
We continue to innovate our tools and approaches to utilizing GIS in determining hydrologic parameters for use in hydrologic computer modeling in HEC-GeoHMS; channel cross sections for use in HEC-GeoRAS, Watershed Modeling with the ArcHydro Extension; Inundation and Special Flood Hazard Area Mapping with the Spatial Analyst Extension; and creating visually stunning presentations with the 3D Extension.
Special Flood Hazard Area Mapping to FEMA DFIRM standards
Grounds Anderson performed floodplain delineation and mapping with ArcView 9.1 to FEMA DFIRM specifications for Cypress Creek (52 miles), Spring Creek (70 miles) and Little Cypress Creek (22 miles) in Harris County, Texas. As project manager for this effort, they reviewed the HEC-RAS models for each watershed in preparation of mapping. Bridge modeling techniques had to be modified to correct for negative surcharges. Once the preliminary floodplain was produced it was carefully checked against the accepted FEMA appeals and protests to ensure that everything was carefully incorporated. GIS mapping techniques were used to ensure that the Special Flood Hazard Areas were a seamless product and no gaps were present. The base topographic data for the mapping was a Digital Elevation Model on a 15-foot grid from LiDAR data compiled county-wide. Grounds Anderson is very familiar with mapping on such base data. The floodway, 1% floodplain and 0.2% floodplain were carefully shaped together to ensure a uniform product. Base Flood Elevations were placed along the studied stream in even increments. Geodatabases were created for use by the community which included all digital products of this mapping effort. Grounds Anderson was responsible for developing the Flood Insurance Study elements for the Hydraulic modeling effort including Floodway Data Tables and Study Profiles. Grounds Anderson was responsible for coordinating the review of the DFIRMs through Michael Baker Jr. Inc. to ensure acceptance of the efforts.
Hurricane Ike Disaster Recovery Mapping
In the days immediately after Hurricane Ike, Grounds Anderson assisted the Harris County Flood Control District with inundation maps for Brays Bayou, Little Cypress Creek, and Willow Creek in Harris County. These inundations were mapped along the main stem of each channel. Inundation grids were successfully calculated using water surface elevation provided by Harris County Flood Control District and were delivered back to the district within 3 working days. All digital data was complied and shipped back to the district with exhibits and completed ESRI personal geodatabases.
San Antonio Land Use and Land Cover Mapping – San Antonio and Bexar County, Texas
As part of team of GIS Professionals, Grounds Anderson prepared Land Use and Impervious Cover maps for approximately 260,000 parcels or half of Bexar County (630 square miles). Utilizing the ESRI products ArcGIS ArcINFO 9.x and the Spatial Analyst helped keep existing topology, and derive complex Map Algebra expressions that enabled us to preserve database information. The Impervious Cover feature data sets were intersected and dissolved using the BCAD parcel data as a backbone. For parcels with areas less than 1 acre where the remotely sensed, multi-spectral data was at an insufficient resolution; parcels were assigned predetermined impervious cover values. Countywide land use for 16 categories was derived from Bexar County Appraisal District data where available land use codes were extracted from their database. The contiguous land use polygons were then intersected with SSURGO Soils Data and Geologic Features related to Aquifer Recharge such as Recharge and Transition Zones. These maps, geodatabases, and feature datasets are suitable for use in floodplain modeling, water quality analysis, watershed management, and storm water fee development. Grounds Anderson prepared and delivered all maps, geodatabases, and feature datasets in NAD83 State Plane, Texas South Central. We prepared a Letter Report summarizing description of data, analysis techniques, and results and findings.
Texas Department of Transportation Outfall Tracking System (OTS) Implementation – State of Texas
As a subcontractor to PBS&J, Grounds Anderson prepared the OTS End User’s Manual, Volume I – End User Documentation which contained documentation for the entire OTS software application including detailed sections for each functional component. We documented the following components of the Data Manager functionality including searching for outfalls and crossing points, reporting, OFDC upload, Laboratory data upload, Desktop mapping data upload, Hydrology data upload, Geodatabase domain update and Data manager change tracking. We also detailed how to use the Map Viewer tool including GIS functions to generate maps and ways to find outfall data graphically. Grounds Anderson was also responsible for testing for Quality Assurance/Quality Control (QA/QC) for various applications of the OTS website. The Desktop Mapping Application allows users the ability to upload and append Geodatabase records which will be automatically symbolized in the Map Viewer and uploads data collected during desktop mapping to the master OTS Geodatabase. The Hydrology Upload Function was also tested. This web-based function allows users to upload non-spatial files of hydrology flow data by outfall, crossing point and specific peak flow estimates associated with defined rain event sizes to the OTS website. Once the data is uploaded users can also append the hydrologic data. The Laboratory Upload Function was tested to ensure that non-spatial laboratory data associated with field data collection could be properly uploaded into the master OTS Geodatabase and appended by the user. The Geodatabase Domain Update Application was tested in an ArcSDE environment. This application allows authorized users an automated method for updating the Master OTS Geodatabase domain tables and the OTS “D” tables simultaneously during update and maintenance operations. The Data Manager Change Tracking Function was tested to ensure that all changes to the OTS Geodatabase and properly recorded. This function will assist with regulatory compliance and provide security against unauthorized data modifications. Modifications were made to the OTS Geodatabase records and the change tracking logs and notifications were carefully examined to ensure that everything was recording properly.