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PART 1 - INTRODUCTION TO SITES B. History and Focus of the SITES Software and its Application

PART 1 - INTRODUCTION TO SITES B. History and Focus of the SITES Software and its Application. SPECIALTY WORKSHOP: SITES TRAINING AND INTRODUCTION TO WINDAM ASDSO Dam Safety 2008. SEMINAR OBJECTIVES. History of NRCS dam design Evolution of the software tools used by USDA

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PART 1 - INTRODUCTION TO SITES B. History and Focus of the SITES Software and its Application

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  1. PART 1 - INTRODUCTION TO SITES B. History and Focus of the SITES Software and its Application SPECIALTY WORKSHOP: SITES TRAINING AND INTRODUCTION TO WINDAM ASDSO Dam Safety 2008

  2. SEMINAR OBJECTIVES • History of NRCS dam design • Evolution of the software tools used by USDA • What is unique about SITES

  3. Farm Pond Design • From the late 1930s the experience the agency gained from the design of farm ponds was transferred to the design of small watershed structures in the late 1940s.

  4. USDA Small Watershed Program • Public Law 78-534 – Flood Control Act of 1944. • 1952 Appropriation Act that authorized 62 pilot watershed projects in 36 states • Public Law 83-566 – Watershed Protection and Flood Prevention Act of 1954.

  5. Watershed Project Locations

  6. Watershed Dams

  7. INLET CHANNEL CREST AUX.. TOP DAM EXIT CHANNEL TAILWATER ELEV TOP DAM CREST AUX. FBH SDH PSH PERM. POOL CONDUIT TAIL- WATER AUX. SPLWY. PERM, POOL DESIGN FLOW (SDH) EXIT CHANNEL INLET CHANNEL CREST PS TAIL- WATER

  8. Criteria for Design • Each of the 6 regions in SCS used their own criteria for design until about 1957 when Eng. Memo 3 was issued. • Eng. Memo. 27 (Rev) for design of small dams was issued in 1965. • TR60 replaced Eng. Memo. 27 in 1976. • (Rev. 1985, Amended 1990, Rev. 2005)

  9. TR-60 Overview • General (Dam Classification, breach discharge, utility cables, pipelines, etc.) • Hydrology • Sedimentation • Geologic Investigations • Earth Embankment and foundations • Principle spillways • Auxiliary Spillways

  10. TR-60 Overview • General (Dam Classification, breach discharge, utility cables, pipelines, etc.) • Hydrology • Sedimentation • Geologic Investigations • Earth Embankment and foundations • Principle spillways • Auxiliary Spillways

  11. Hazard Classification and Risk • From the late 1950s the criteria allowed greater risk with low hazard structures than it did with high hazard structures. CLASSES OF DAMS Low Hazard Class Significant Hazard Class High Hazard Class

  12. Hand Flood Routing

  13. Hydrology • Spillway discharge and floodwater storage criteria • Design Hydrographs • Principle Spillway Hydrograph • Stability Design Hydrograph • Freeboard Hydrograph • Dams in Series

  14. Auxiliary Spillways • Convey excess water through, over, or around a dam. • Usually open channels excavated in natural earth, earthfill, and/or rock. • Must pass the SDH at safe velocities and meet allowable effective stress. • Must pass the FBH at water levels < the top of dam and not breach.

  15. Mainframe Computer Routing • Mainframe Computer Programs were developed in the 1960s to replace hand routing methods. • PSIN for Principal Spillway INput and REServoir INput routine RSIN were used through the 70s • Dams and Dams2 were used concurrently with PSIN and RSIN.

  16. SITES TIME LINE SITES 2005.1.3 October 2007 2005 SITES 2000 – Sites in Series SITES 98.1.1 (Windows Version with IDE) 1995 21 new Control Words added to Dams2 Design & Analysis of Earth Spillways Team DAMS2 PC Test Version 1985 Emergency Spillway Flow Study Task Group Interim Version DAMS2 & Manual 1975 DAMS2 DAMS 1965

  17. PC VERSIONS • In 1989 the first DOS PC version of Dams2 was released as a test version. • SITES – Stability & Integrity Technology for Earth Spillways. (Name change 1994) • In 1998 the first windows version of SITES was released.

  18. TR – 52 A Guide for Design and Layout of Earth Emergency Spillways (1973) Bulk Length = Bu & Resistance > Attack? Inlet Channel Exit Channel 1 Control Section 1 Sd Su 2 ft. 2/Su L 2/Sd Longitudinal Bulk Length = Bu Bu = L + 2/Su + 2/Sd L = Length of level section of spillway in ft. Su = slope of upstream part in ft./ft. Sd = slope of downstream part in ft./ft.

  19. 1983 -The ESFSTG was formed 1991 - ARS & SCS established DAES Team

  20. Earth Spillway Flow Study Task Group(ESFSTG) • Established in January 1983 • Assignment - Visit dams with major spillway flows or damage - Gather spillway performance data\ - Analyze data - Prepare performance reports • Group - Civil Engr., Geologist, Hyd. Engr.

  21. Performance of ESFSTG • From 1983 to 1991, SCS had spillway flow at over 1450 sites. • ESFSTG and ARS visited approximately 125 sites. • 10 spillway performance reports were published.

  22. Dam height Spillway width Exit channel slope Exit condition Spillway materials Maintenance 20 - 140 feet 20 - 500 feet 2 - 16 % Good to vert. Drop Rock to sand Excellent to very poor Range of Sites

  23. Reservoir head above crest Maximum velocity Flow duration Total discharge / bottom width (oe/b) 0.4 - 8.9 feet 5 - 17 ft. / Sec. 8 - 124 hours 1 to 91 AF / ft. Range in Flow Parameters

  24. Observed Conditions at the Sites • Most spillways functioned as intended • A few spillway crests breached (4 sites, 1 drained pool) • Some dams overtopped (8 sites, 0.3 to 1.5 ft.)

  25. LABORATORY SPILLWAY MODEL • Flow concentration • Failure vegetal covers • Surface detachment processes • Headcut migration.

  26. Design and Analysis of Earth Spillway Team (DAES) • Joint ARS/SCS team • Established in July 1991 • Purpose - To develop a model to predict breach potential for earth spillways • Team members - ARS: Temple and Hanson - NRCS: Moore and Brevard

  27. DAES Study Purpose • Study spillway performance • Evaluate spillway design criteria • Revise criteria where necessary • Incorporated spillway erosion model into DAMS-2 resulting in SITES

  28. SITES ? ? ? • Watershed Rainfall-Runoff • Streamflow routing • Reservoir Routing • Principal spillway rating • Auxiliary spillway rating • NRCS dam design features • Earth Spillway Analysis

  29. SITES • Able to route 3 Hydrographs at a time. • Principal spillway – PS • Auxiliary spillway – SDH • Freeboard -- FBH

  30. SITES • The program will provide the user with a principal spillway rating for a set of standard NRCS risers. • The rating assumes a free outlet for the principal spillway conduit. • A standard riser has the dimensions of Dx3D.

  31. SITES • The program has the ability to rate a vegetated earth spillway in either critical or subcrital flow. • Mixed flow is also allowed between vegetated and nonvegetated reaches in the spillway.

  32. Auxiliary Spillway Profile Constructed Inlet Channel Constructed Exit Channel Inlet Natural Ground Tie Sta. Exit Natural Ground

  33. SPILLWAY SURFACE , ft ELEVATION STATION , ft

  34. STABILITY • The tractive stress of the vegetated earth spillway is computed from the 6 hour SDH storm.

  35. INTEGRITY • This is the design to make sure the spillway does not breach from the FBH storm. • This requires geologic information from the entrance of the spillway through the valley floor. Valley floor is the lowest point where erosion begins.

  36. THE END

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