development and floodplain delineation (CRWR-FloodMap and HEC-GeoRAS), and lumped parameter hydrologic modeling and steady flow hydraulic analysis (HEC-HMS and HEC-RAS). Anderson’s investigation was a first attempt for TxDOT at automating this entire process and for representing the spatial variability of the watershed characteristics, integrating hydrologic and hydraulic modeling processes with GIS, and displaying an accurate floodplain map of the project site.
The initial scope of the author’s project was to implement a study in a different area of Texas and apply the same methodology as Anderson (2000). However, after Anderson’s study was completed TxDOT noted that the watershed lag time values calculated using CRWR-PrePro for input into HEC-HMS for the Castleman Creek (in McLennan County, Texas) watershed were over four times greater than the values calculated previously for a TxDOT hydrologic model of
the area. Anderson’s
At this point it became evident that automated hydrologic study need to be
some assumptions further investigated.
used in Figure
1.1 gives an example of automated methods and
the large differences calculated by Anderson (2000) using TxDOT using traditional, paper map-based methods.