Watershed Assessments / Studies
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City of Austin Technical Procedures Manual for Watershed Erosion Assessments, 1997
With the knowledge of new urban development greatly accelerating stream channel erosion as a result of the increase in frequency, duration and peak flow in channels, the City of Austin, Drainage Utility Department requested Raymond Chan and Associates, Inc. (RC&A) to prepare this Technical Procedures Manual as a guideline for the completion of the Watershed Erosion Assessments for 17 watersheds. The Watershed Erosion Assessments will be one component of a watershed master plan for each watershed.
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City of Austin Regulatory Approaches for Managing Stream Erosion, 1997
Literature review, storm modeling, field review. Determined that the frequent storm events appear to cause the bulk of channel erosion. Channel forming flow may be in the range of the 6-month storm for highly developed watersheds. Management approach would be water quality ponds with 1/2 + 0.1 rule or larger storage volumes. Volume control to manage peak and duration most effective.
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City of Austin Watershed Erosion Assessments for 17 Watersheds, 1997
Most of the Austin’s watersheds, including urban and suburban watersheds, are drained by streams that exhibit existing creek bank erosion problems and have the potential for future creek bank degradation. The concern for future creek bank failures, long term channel degradation, and their impact to creekside residents and water quality initiated the City of Austin Drainage Utility Department to authorize the city wide watershed erosion assessments in January 1997. The 17 watersheds are as follows:
Barton Creek Watershed
Blunn Creek Watershed
Boggy Creek Watershed
Bull Creek Watershed
Buttermilk Creek Watershed
Country Club Creek Watershed
East Bouldin Creek Watershed
Fort Branch of Boggy Creek Watershed
Johnson Creek Watershed
Little Walnut Creek Watershed
Shoal Creek Watershed
Tannehill Branch of Boggy Creek Watershed
Waller Creek Watershed
West Bouldin Creek Watershed
Walnut Creek Watershed
Williamson Creek Watershed
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City of Austin Lower Walnut Creek Erosion Management Facility Study
The Walnut Creek Watershed Erosion Assessment predicted that the lower portion of Walnut Creek from Dessau Road to the Colorado River would experience the most channel enlargement of all the City of Austin Phase I watersheds. This is due to the more than doubling of the watershed impervious cover and the highly erosive alluvial soils. To manage channel erosion in this reach, the City of Austin proposed the Lower Walnut Creek Erosion Management Facility upstream of Sprinkle Road. The intended purpose of the facility is to manage channel erosion to prevent downstream channel enlargement.
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City of Austin Onion Creek Watershed Erosion Assessment
A study to assess the erosion related characteristics of Onion Creek from the Hays/Travis County Line to the Creek’s confluence with the Colorado River. The total stream study length was approximately 27.9 stream miles. This Study followed the analytical guidelines established in the “Technical Procedures for the Watershed Erosion Assessments” prepared by Raymond Chan & Associates, Inc. in 1997.
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Watershed Restudy, Gilleland, Elm and Decker Creeks, Austin, Texas
Assisted in the development of digital geo-referenced hydrologic and hydraulic models and floodplain maps for the Gilleland, Decker, and Elm watersheds for both existing and future land-use conditions. RC&A was responsible for the hydrology portion of Elm Creek (basin area of 8.4 square miles). RC&A performed hydrologic analysis and developed digital geo-referenced hydrologic model by integrating the uses of the widely used programs: ESRI ArcView GIS, HEC-GeoHMS, and HEC-HMS; prepared the Elm hydrologic Technical Support Data Notebook, which documented the hydrologic analysis and provided all applicable support date (i.e. hydrologic workmap, HEC-HMS model, etc.). RC&A also developed peak discharges for the 2-, 5-, 10-, 25-, 50-, 100-, 250- and 500- year storm events and assessed potential Regional Detention Facility and/or Diversion Structure sites for Elm Creek to reduce flooding impacts.
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