Geographic Integration of Modeling Systems:
The Map To Map Application
Oscar Robayo, CRWR
Table of Contents
Water resources planning and management relies heavily on engineering models. For a timely and systematic operation of this kind of management operations, an information technology framework is needed to streamline the modeling process. Connectivity of all modeling resources represents the main “bottleneck” to be addressed in order to achieve a continuous and operational workflow. The diverse nature of water resources models, file formats and data structures makes this a complex task only possible through new technological advances.
Using ArcGIS 9.0 ArcObjects and the new ModelBuilder environment, a methodology for converting a NEXRAD rainfall map time series to a floodplain map has been developed. The methodology integrates HEC-HMS and HEC-RAS modeling systems through flow change points in the stream network georeferenced in the Arc Hydro data model for water resources. The coupling of these external modeling systems via a common geographic framework enables dynamic and seamless end-to-end simulations for real time and planning operations. The integrating approach has been implemented in the San Antonio River basin, Texas, as part of a Regional Watershed Modeling System (RWMS) being developed by the San Antonio River Authority (SARA), the City of San Antonio, and Bexar County. The Salado and Rosillo creeks were used to test a prototype version of the envisioned modeling framework.
ObjectivesTo explore a spatial framework as the common ground for the model connectivity
To provide building blocks for a comprehensive watershed management tool
To support the efficient management and distribution of datasets and model configurations
To efficiently update models to remain current with land use changes
To facilitate regional planning and prioritization of water resources projects
To provide a single repository of spatial and modeling data to be used by all end users
To facilitate automated floodplain mapping
To facilitate floodplain updates in the form of DFIRMs based on design storms
To provide support for near real time flood forecasting
To provide support for analysis of historic rainfall events
The main modeling resources needed to be connected to achieved the automation of all the integrated processes were first defined based on traditional engineering practice and a variety of existing modeling resources. The proposed system should be able to acquire NEXRAD map time series to drive hydrologic simulations in HEC-HMS whose streamflow outcome will feed the hydraulic model HEC-RAS that provides the needed water surface elevations to perform the final floodplain delineation to get the flood inundation map. For this, 9 components were identified:
Reading Precipitation Time Series Records
NEXRAD radar precipitation data for the Hydrologic Rainfall Analysis Project (HRAP) grid (a square-celled mapgrid) is read from a series of text files containing hourly data for a storm event on July 01, 2002. The text files are read and the time series are transferred to geodatabase tables with Arc Hydro format (TimeSeries and TSTypeInfo tables) as well as a HEC-Time Series Type table to store the HEC-DSS descriptors of the data.
Mapping Time Series to Watersheds
The Time Series records associated to NEXRAD cells are map to the Watersheds to assign a hyetograph for the rainfall-runoff transformations in HEC-HMS. The time series transfer operation is done by means of an intersection layer generated from the NEXRAD and watershed polygons. By computing the NEXRAD cell area (areally weighted process) inside a given watershed polygon the tool estimates the average rainfall over the watershed.
Transferring Time Series to HEC-DSS
Once the precipitation records have been reassigned to the watersheds they are transferred from geodatabase time series tables to HEC-DSS binary format based on the HEC-DSS Time Series Type table with the needed arguments for the transfer process. Also, the project, flow, and plan files are updated to set up a new run configuration.
Executing HEC-HMS
A previously set HEC-HMS model for the basin is called with reference to the previous precipitation records now stored in the HEC compatible HEC-DSS system. The execution of HEC-HMS is done through a batch file with the project file and proper RUNID as input parameters.
Transferring the Flow Records to Geodatabase
The output flow discharges from HEC-HMS corresponding to watershed outlet points that in turn represent flow change locations (Cross Sections) in HEC-RAS are transferred to the Geodatabase.
Executing HEC-RAS
A previously set HEC-RAS model for the river system is called with reference to the previous flow change location records. The execution of HEC-RAS is done through the HEC-RAS object library that exposes some execution and writing functionalities.
Post-processing steps for Floodplain Delineation
The Map2Map application is still a work in progress and some refinements are being developed. More generic methodologies approaches are being defined to facilitate its implementation over any given case study.
These materials may be used for study, research, and education, but please credit the authors and the Center for Research in Water Resources, The University of Texas at Austin. All commercial rights reserved. Copyright 2003 Center for Research in Water Resources.