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Understanding Gully Formation in Bolin Creek Watershed for Future Prevention

Explore gully formation factors, mapped soil types, and outlet considerations to predict gullies in Bolin Creek Watershed. Impervious cover, stream power, and soil erodibility play crucial roles. Recommendations detail key parameters for Orange County's gully prevention efforts.

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Understanding Gully Formation in Bolin Creek Watershed for Future Prevention

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  1. Identifying gullies in bolin creek watershed Christina Hurley Alyssa James CarlyBuch Nicole Meyer

  2. Introduction to Gullies • What is a Gully? • Where do Gullies occur?

  3. Flow Chart

  4. Soils

  5. Factors that affect soil erodibility • Particle Size • Organic Matter Content • Plant/vegetation and animal life • Climate • Land Management • Slope and length of slope • Precipitation

  6. Mapped Gully Soil Types

  7. K Value as an indicator

  8. T Factor as an Indicator

  9. Outlets that fall in high K values and high T factors

  10. Considering other factors • Slope >10 • Loamy soils • High Runoff • Poor Drainage Class

  11. Outlet Wastersheds

  12. Digitizing Outlets and Calculating Watersheds

  13. Outlet Watersheds

  14. Outlet Watersheds

  15. Outlet Watersheds

  16. Outlet Watersheds

  17. Outlet Watersheds Near Gullies

  18. Stream Power

  19. Stream Power and Outlets

  20. Impervious Cover has Larger Influence than Slope Flow accumulation weighted by impervious cover Slope

  21. Stream powers at outlets and existing gullies 416 1406

  22. Stream powers at outlets 1393

  23. Stream Powers and Outlets 307

  24. Conclusions • Existing gullies were not by outlets with large watersheds, or with necessarily high stream powers • Means that it is difficult to predict where gullies will form • A larger sample size of existing gullies might yield more conclusive results • Impervious cover had a more significant influence on stream power that slope overall • Outlets with a higher stream power going into the outlet were more likely to have gullies (there or below the outlet) • Soil T-factor has strong influence on the formation of gullies

  25. Future Considerations • In order for Orange County to prevent further gullies from forming they should continue to watch: • Present soil mass movement and rate • Parent material • Cemented, compacted or impermeable subsoil layers • Area impervious upstream • Size of watershed • Stream power • Root distribution • Vegetation type and distribution • Saturated hydraulic conductivity • Pore water pressure • Precipitation occurrence an distribution • Temperature fluctuations • Degree of weathering • Dips parallel to slopes along streams • Summarized from Brooks, 1997

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