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<br />The City of Sumas, located in northern Washington at the U-S, / Canadian border experiences extensive flooding from overflows from the
<br />Nooksack River, During extreme floods on the river, floodwaters overflow from the channel into an adj acent watershed and flow northward
<br />through the City of Swnas and into Canada, During extreme flood events, much of Swnas is inunWlted as floodwaters follow a complex
<br />network of flow paths through the city, To identify areas of greatest flood hazard and plan for fuulre development, the city prepared a
<br />Floodplain Management Plan. The Plan included an evaluation of alternatives to mitigate the impacts of flooding. The alternatives included
<br />bypassing the flood around the city, creating a flow corridor through the city, changing zoning within the city to better represent high hazard
<br />areas, establishing a buy-out cOlridor, and selecting specific properties for buy-out in the future. A 2-dimensional hydraulic model,
<br />FESWMS, was developed to simulate the complex flow patterns through the city. The hydraulic modeling results were integrated with GIS
<br />to produce graphic illustrations that were more meaningful to decision-makers in the city, Integration of model results and GIS produced
<br />color maps with planimetric data, such as roads, parcels, and railroads; depth of flooding shown as wlor gradations; and velocity vectors
<br />showing direction and speed of floodwater through the city, A series of maps were prepared for each alternative considered by the city and
<br />the impacts of each on flood levels and flow paths were readily observable, The layering of modeling results with parcels and local
<br />landmarks allowed city officials to easily interpret the results of technical analysis, A preferred flood mitigation alternative was selected that
<br />included defining a special flood risk zone, rezoning segments of the city to preserve open space in flood hazard areas, and identifying two
<br />corridors for buy-outs of structures in the future, The 2-dimensional hydraulic modeling results were submitted to FEMA with a request
<br />to revise the floodplain map for the city,
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<br />DEVELOPMENT OF THE CHARLOITE WATERSHED MANAGEMENT SYSTEM: INTEGRATING GIS WITH
<br />HYDOLOGIC & HYDRAULIC MODELING
<br />Joseph R Chapman, PE, Anthony R Dudley and Jeffrey S, Buckalew
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<br />One of the largest challenges facing rapidly growing conununities is regulating and managing the stormwater infrastructure system, Ai; a
<br />community continues to grow, changes to the drainage infrastructure occur on a daily basis, Many communities will develop a traditional
<br />"master plan" that will outline significant improvements needed in a watershed, intended to be constructed in a priority order over many years
<br />or even decades as funding allows. However, these recommendations are based on a snapshot of conditions that existed at a particular time,
<br />and cannot consider ever changing conditions including continued development, new planning strat'egies and goals, etc. The master plan
<br />becomes more and more out of date as time passes and conditions change. and the large amount of engineering resources invested in its
<br />preparation are largely lost. The City of Charlotte and Mecklenburg County have developed an alternative to the traditional master plan
<br />which would allow for a continuos "living" master plan, designed to minimize the up-front cost and maximize the usefulness and flexibility
<br />of the planning process over time. The City decided to pursue the development of a fully integrated modeling and GIS system that would
<br />reduce the effort involved in developing hydrologic & hydraulic models, allowing for more frequent updates and assessing development
<br />impacts early in the planning stages, When complete, the City will have a comprehensive Watershed Management System in place that will
<br />allow for ongoing modeling and model upkeep to be done by in-house staff on a routine basis. The, system will also provide an intenace
<br />to allow non-modelers to access and utilize the results for use in planning and design of drainage improvements, This paper and presentation
<br />will demonstrate the automation capabilities touch on issues related to data maintenance and ease ,)1' mtenace with various hydrologic and
<br />hydraulic programs.
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<br />INTEGRATING GEOGRAPillC INFORMATION SYSTEMS (GIS) AND WATERSHED MODELING
<br />David p, Preusch, P,E, and Chris Krebs
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<br />The integration of Geographic Information Systems (GIS) and watershed modeling is moving hydrologic and hydraulic analysis to a new
<br />dimension. What was once was a tedious process of defining drainage boundaries on topographic maps, measuring hydrologic parameters
<br />from soils and land use maps, and inputting this information in a hydrologic model can now be automated using Digital Terrain Models
<br />(DIMs) and GIS technology. Digital information needed to penorm this analysis is becoming more and more available from government
<br />agencies, DBMs, Land Use Land Cover (LULC) information., and digital orthophotographs are now available for many areas in the United
<br />States from the USGS. Soil infunnation is available from the NRCS at the state and county level. Defining rainfall distribution (both spatial
<br />and temporal) for model calibration has become much more accurate through the use ofNEXRAD data which is available from the NWS
<br />and other commercial providers, Programs are available which link the digital watershed data to hydrologic models, These programs include
<br />\VMS (Watershed Modeling System) from the Engineering Computer Graphics Lab at Brigham Young University. This presentation will
<br />demonstrate how a HEC-I model was developed using WMS for the Crooked Creek watershed in Putnam County, West Virginia. The
<br />demonstrations will show how GIS is used to preprocess watershed data, how watershed bound.,ies are delineated and drainage areas
<br />calculated from a DEM, how Runoff Curve Numbers (RCNs) are generated, and how runoffhydrographs are developed and displayed,
<br />Other applications and advantages of using GIS in watershed modeling will be discussed.
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