Chan Partners Engineering


Chan & Partners Engineering, LLC

Consulting Civil Engineers


Watershed Assessments / Studies


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 Chan & Partners Engineering, LLC (CPE) 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.

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.

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

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.

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.

Watershed Restudy, Gilleland, Elm and Decker Creeks, Austin, Texas

Gilleland, Elm, Decker 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. CPE was responsible for the hydrology portion of Elm Creek (basin area of 8.4 square miles). CPE 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.). CPE 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.

North Fork Dry Creek East Floodplain Study & Mapping, Austin, Texas

North Fork Dry East The Dry Creek East watershed, including the North Fork and the South Fork Watersheds, is a suburban watershed with approximately 55 square miles of drainage area and 45.8 stream miles. The watershed is bordered roughly by the Colorado River on the east, Onion Creek on the north, Marble Creek on the west, and Maha Creek on the south. The creek discharges into the Colorado River. The main purpose of this project is to develop digital geo-referenced hydrologic and hydraulic models and floodplain maps for the Dry Creek East watershed for both existing and future land-use conditions in accordance with City of Austin (COA) and FEMA requirements. CPE is responsible for the hydraulic portion of North Fork Dry Creek (study length of 4.2 miles). Developed the North Fork hydraulic models, floodplain maps, hydraulic Technical Support Data Notebook (TSDN), bridge photos, CAD profiles and LOMR applications. Performed hydraulic analysis and developed digital geo-referenced hydraulic model.

Bull Creek Watershed Floodplain Modeling and Mapping, Austin, Texas

Bull Creek Watershed The Bull Creek watershed, including West Bull Creek, is a suburban watershed with approximately 31.5 square miles of drainage area and 34.25 stream miles to be studied. The main purpose of this project is to develop digital geo-referenced hydrologic and hydraulic models and floodplain maps for the Bull and West Bull Creek watersheds for both existing and fully-developed land-use conditions. As a subconsultant to Halff Associates (HA), CPE’s responsibility for this project involved developing hydraulic data and perform floodplain mapping for selected tributaries of Bull Creek. CPE developed fully-annotated HEC-RAS models with all supportive GIS files such as cross-sections and GIS geodatabase for both existing and fully-developed land-use conditions, produced digital hydraulic data including tables, methodology descriptions and exhibits for Existing and Fully-Developed Land-use Conditions to incorporate into the Hydraulic Technical Support Data Notebooks (TSDN), produced water surface elevation profiles at similar vertical and horizontal scale as the profiles in the effective FIS report for selected FEMA flood frequencies using RAS-PLOT for the detailed study tributaries only, and performed floodplain mapping and submitted digital copies of the floodplains and BFEs for the detailed study tributaries for both existing and fully-developed land-use conditions.

Carson Creek Watershed Floodplain Modeling and Mapping, Austin, Texas

Carson Creek Watershed Carson Creek is a suburban watershed with a drainage area of 6.04 square miles and 8.25 miles of streams to be studied. The watershed is bordered roughly by the Colorado River to the northeast and is centered on and dominated by the US 183 and State Highway 71 interchange. The creek discharges into the Colorado River. Develop digital, geo-referenced hydrologic and hydraulic models and floodplain maps for both existing and fully-developed land-use conditions. As a subconsultant to ATKINS, CPE developed the subbasin delineations, time of concentration, runoff curve numbers and other HEC-HMS input parameter for the existing land-use condition HEC-HMS model for 2-year through 500-year return periods (Q2-Q500). CPE produced hydrologic data including tables, methodology descriptions and exhibits in digital format for Existing Land-use Condition for ATKINS to incorporate into the Hydrologic TSDNs.

Cottonmouth Creek Watershed Floodplain Modeling and Mapping, Austin, Texas

Cottonmouth Creek Watershed Cottonmouth Creek is a suburban watershed with a drainage area of approximately 5 square miles and 7 miles of streams to be studied. The watershed is bordered roughly by the South Fork Dry Creek East Watershed on the south, Onion Creek Watershed on the north, Marble Creek Watershed to the west and North Fork Dry Creek East Watershed on the east. The creek discharges into Onion Creek. Develop digital, geo-referenced hydrologic and hydraulic models and floodplain maps for both existing and fully-developed land-use conditions. As a subconsultant to ATKINS, CPE developed the subbasin delineations, time of concentration, runoff curve numbers and other HEC-HMS input parameter for the existing land-use condition HEC-HMS model for 2-year through 500-year return periods (Q2-Q500). CPE produced hydrologic data including tables, methodology descriptions and exhibits in digital format for Existing Land-use Condition for ATKINS to incorporate into the Hydrologic TSDNs.

Boggy Creek Watershed Floodplain Modeling and Mapping, Austin, Texas

Boggy Creek Creek Watershed The Boggy Creek watershed, including Tannehill Branch and Fort Branch, is an urban watershed with a drainage area of approximately 14 square miles and 24 miles of streams to be studied. The watershed is bordered roughly by the Colorado River to the south, IH 35 to the west, US Hwy 290 on the north and US Hwy 183 to the East. The creek discharges into the Colorado River.Develop digital, geo-referenced hydrologic and hydraulic models and floodplain maps for both existing and fully-developed land-use conditions. As a subconsultant to ATKINS, CPE developed the subbasin delineations, time of concentration, runoff curve numbers and other HEC-HMS input parameter for the existing land-use condition HEC-HMS model for 2-year through 500-year return periods (Q2-Q500). CPE produced hydrologic data including tables, methodology descriptions and exhibits in digital format for Existing Land-use Condition for ATKINS to incorporate into the Hydrologic TSDNs.