PART 1 - INTRODUCTION TO SITESPART 1 - INTRODUCTION TO SITES

B. History and Focus of the SITES B. History and Focus of the SITES Software and its ApplicationSoftware and its Application

SPECIALTY WORKSHOP: SPECIALTY WORKSHOP: SITES TRAINING AND SITES TRAINING AND

INTRODUCTION TO WINDAM INTRODUCTION TO WINDAM

ASDSO Dam Safety 2008ASDSO Dam Safety 2008

SEMINAR OBJECTIVES

• History of NRCS dam design

• Evolution of the software tools used by USDA

• What is unique about SITES

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.

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.

Watershed Project Locations

Watershed Dams Constructed by Year

0

100

200

300

400

500

600

700

Year

Num

ber o

f Dam

s

PL-566Pilot/RC&D

PL-534

Watershed Dams

PERM,POOL

TAIL-WATER

TOP DAM

CREST AUX.

PERM. POOL

FBH SDH PSH

CONDUIT

CREST PS

DESIGN FLOW (SDH)

TAIL-WATER

AUX. SPLWY.

EXIT CHANNELINLET CHANNEL

TOP DAM

INLET CHANNEL

EXIT CHANNEL

TAILWATER ELEV

CREST AUX..

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)

TR-60 Overview

• General (Dam Classification, breach

discharge, utility cables, pipelines, etc.)

• Hydrology

• Sedimentation

• Geologic Investigations

• Earth Embankment and foundations

• Principle spillways

• Auxiliary Spillways

TR-60 Overview

• General (Dam Classification, breach

discharge, utility cables, pipelines, etc.)

• Hydrology

• Sedimentation

• Geologic Investigations

• Earth Embankment and foundations

• Principle spillways

• Auxiliary Spillways

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 DAMSLow Hazard ClassSignificant Hazard ClassHigh Hazard Class

Hand Flood Routing

Hydrology

• Spillway discharge and floodwater storage criteria

• Design Hydrographs– Principle Spillway Hydrograph– Stability Design Hydrograph– Freeboard Hydrograph

• Dams in Series

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.

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.

Design & Analysis of Earth Spillways Team

SITES TIME LINE

1965

2005

1985

DAMS

DAMS2

Interim Version DAMS2 & ManualEmergency Spillway Flow Study Task Group

DAMS2 PC Test Version

21 new Control Words added to Dams21995

1975

SITES 98.1.1 (Windows Version with IDE)

SITES 2000 – Sites in Series

SITES 2005.1.3 October 2007

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.

Bulk Length = Bu & Resistance > Attack?

TR – 52 A Guide for Design and Layout ofEarth Emergency Spillways (1973)

Sd

Inlet Channel Exit Channel

11Su 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.

Control Section

1983 -The ESFSTGwas formed1991 - ARS & SCS established DAES Team

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.

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.

Range of Sites• 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 in Flow Parameters

• 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.

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.)

LABORATORY SPILLWAY MODELLABORATORY SPILLWAY MODEL

•Flow concentration

•Failure vegetal covers

•Surface detachment processes

•Headcut migration.

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

DAES Study Purpose

• Study spillway performance

• Evaluate spillway design criteria

• Revise criteria where necessary

• Incorporated spillway erosion model into DAMS-2 resulting in SITES

SITES ? ? ?SITES ? ? ?

•Watershed Rainfall-Runoff

• Streamflow routing

• Reservoir Routing Principal spillway rating Auxiliary spillway rating NRCS dam design features

• Earth Spillway Analysis

SITES

• Able to route 3 Hydrographs at a time.

• Principal spillway – PS

• Auxiliary spillway – SDH

• Freeboard -- FBH

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.

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.

Auxiliary Spillway ProfileAuxiliary Spillway Profile

InletNaturalGround

ConstructedInlet Channel Constructed

Exit Channel

Exit Natural Ground

Tie

Sta

.

SPILLWAY SURFACE

STATION

EL

EV

AT

ION

, ft

, ft

STABILITY

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

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.

THE END