MILL CREEK WATERSHED STUDY: INNOVATIVE GIS TECHNIQUES FOR EFFICIENT MASTER PLANNING SOLUTIONS

Due to rapid urban sprawl, Johnson County, Kansas, has embarked on an aggressive program to complete stormwater master plans and new floodplain delineations county-wide. The primary goals of the project are to: develop new hydrologic and hydraulic models for both existing and ultimate development conditions; update the existing FEMA floodplain boundaries for existing development conditions; provide local communities with a floodplain management tool; define areas of flood problems; develop sound engineering and bio-engineering solutions to alleviate identified problem areas; and, develop GIS-based stormwater data for ongoing asset management purposes. The project involves the requirement of all data that is developed, including models, survey data, field sketches, and written documents to be stored in a project-based SQLServer database. This requirement changed the overall contextof nearly every portion of the work, from technical memoranda preparation, fieldwork, modeling, and exhibit preparation.Project tasks and components were all linked in some fashion to the project database, utilizing one set of project information. Work flow was arranged to ensure totally integrated information transfer between data collectors, the database, modeling, and mapping. All surveying data that was collected was done so in an automated fashion with data collectors formatted to match the required database input. This information was then uploaded to the database, where various uses were obtained, including model development, mapping, and exhibit preparation.Modeling consisted of HEC-1 for hydrologic analyses, and HEC-RAS for hydraulic analyses. GIS techniques, primarily tools within ArcView and Arc/INFO GIS platforms, were utilized to automate the process of model development, while ensuring that a seamless inflow of fieldcollected data was utilized to generate the models.ArcView and Arc/INFO were used extensively to develop shape files and coverages necessary to perform automated HEC-1 model generation and input data development. HEC-GeoRAS was also utilized to automate the development and generation of information for the HEC-RAS hydraulic models, generating cross sectional and structure crossing information, and building the HEC-RAS models automatically from the database. HEC-GeoRAS was also utilized upon completion of the calibrated modeling efforts to plot out new floodplain mapping, along with ESRI' Spatial and 3-D Analyst tools.