rationale for alternative crossing design approach
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Rationale for Alternative Crossing Design Approach
Marty E. Rye, P.E. Hydrologist
Superior National Forest Lake Superior Watershed Ditch and Culvert Design Workshop
Duluth, MN March 6, 2013
Liability Has Always Been A Part of Design Code of Hammurabi (Babylonian – 1772BC)
229 If a builder build a house for some one, and does not construct it properly, and the house which he built fall in and kill its owner, then that builder shall be put to death.
230. If it kill the son of the owner the son of that builder shall be put to death.
231. If it kill a slave of the owner, then he shall pay slave for slave to the owner of the house.
232. If it ruin goods, he shall make compensation for all that has been ruined, and inasmuch as he did not construct properly this house which he built and it fell, he shall re-erect the house from his own means.
233. If a builder build a house for some one, even though he has not yet completed it; if then the walls seem toppling, the builder must make the walls solid from his own means.
Why is There an “Standard of Practice”?
• Implicit contract with society or ‘social contract’ to provide a level of service…implicit in this is risk management
• Accountability for the performance of the design
• Codified and litigated • Technically the best approach • Tradition
Professional Engineers Work for the Public
Hold paramount the: • safety, • health, and • welfare of the public
Professional Engineering Code of Ethics
Brief History of Culvert and Stream Crossing Design
Sources of information:
Chow, Ven Te. Hydrologic Determination of Waterway Areas for the Design of Drainage Structures in Small Drainage Basins. University of Illinois Experiment Station. Urbana, IL. 1962
McEnroe, Bruce. Historical Design of Bridges and Culverts: A Historical Review. Great Rivers History – ASCE. 2009
Potter, William D, Peak Rates of Runoff from Small Watersheds. Federal Highway Administration. 1961
Willard,E.V. Drainage Areas of Minnesota Streams and Method of Estimating Probable Flood Flows. 1922
Early Discussion (mid 19th century)
1851: Irish engineer Thomas McIvany describes Rational Formula (not widely adopted) 1853: American design textbook, “Greatest quantity of water which they can ever be required to pass and should be at least 18 inches square or large enough to admit a boy to enter to clean them out”
Meyer 1879: Meyer Formula A = C √D where A = area of opening (sq ft) D= drainage area (acres) C = coefficient (1-4) based upon general description of drainage area
(flat, hill, rocky) – developed from observation of judicious gagings in the area….and applied to smaller pipes
• Major E.T.C. Meyer, Chief engineer of the Richmond,
Fredricksburg, and Potomac Railway after the Civil War • Presented at a club in Cleveland in 1879 • Used by railroad engineers in the east and Virginia • Used in Wisconsin and Connecticut as late as 1960’s
1880: Burkl – Ziegler Q = Cr √SA where Q = discharge (cfs) r = rainfall intensity (in/hr) S = watershed slope (ft / 1,000 ft) A = drainage area (ac) C = coefficient generally 0.62,
ranged from 0.31 to 0.75 = (nature of surface)
• Swiss engineer and adopted in US by Rudolph Hering in 1881 in Report to the National Board of Health regarding Sewerage Works in Europe
• No guidance on how to calculate intensity (r) or slope • Used by 8 of 43 states (19%) in 1960’s
Burkl - Ziegler
A.M. Wellington
• 1886: Wellington, “It is natural for fallible man to wish to reduce everything to a rule, even if it be only a rule of thumb. The responsibility of the individual is much diminished if he has something of that kind to lean on, and in so doubtful a matter as the proper sizing of culverts, this is especially natural……..guess at the proper size and double it. We apprehend this formula will give far more satisfactory and trustworthy results”
University of Illinois Professor A.N. Talbot
1887: Talbot Formula A = C (D¾) where A = area of opening (sq ft) D= drainage area (acres) C = coefficient 1/6 to 2/3 based
upon shape of drainage area, snow or rain dominance, land use
• “any formula will be approximate….judgment must be the main dependence, the formula being a guide to it…”
• Physically based as well - Look at the stream, high water marks, and similar streams in the area
• Widespread popularity for railroad and highway engineer
• 1960’s 25 of 43 states used the Talbot formula
Rational Formula…not yet
1889: Kuichling introduced Rational Formula to America (though not in familiar form)
• Again, slow acceptance because there is
no guidance on how to calculate C or i
Dun’s Table • 1890 – 1906: James Dun’s Table (Sante
Fe Railroad) initially in 1890 - revised several times until 1906
• Applied from a few acres to 6,400 sq miles • Illinois to Texas / N. Mexico with several
subregions • Widely adopted by highway engineers • 5 of 43 states still used in the 1960’s
So, in Missouri and Kansas a drainage area of 8 sq miles requires an area of 601 sq ft of bridge area
Civil Engineering Text 1902: A.T. Byrne (A Treatise on Highway Construction) Design factors affecting sizing of drainage structures include: - rate of rainfall - soil condition - inclination of the surface - condition and inclination of the stream bed - Watershed shape and location of tributaries - form of the mouth and culvert bed - is it acceptable to back up water Suggested Design Procedure (field-based)
• look at existing crossings • measure cross-section at high flow • look for high water marks
Describes limitations and error and don’t get concerned about the “mathematical exactness…the real question is whether at 2-ft or and 8-ft pipe is needed”
Minnesota 1922 “Drainage Areas of Minnesota Streams and Method of Estimating Probable Flood Flows”
• Controlling floods, • Developing water powers, • Furnishing water supply for municipal
consumption, • Designing adequate culverts and bridges, • Providing sufficient capacity for drains, and • All kindred problems
Minnesota (E.V. Willard) Department of Drainage and Waters
Q = A 0.6
where, Q = cfs and A = square miles
Correction Coefficient Ranges from 0.35 to 15!
Progression to Present 1917: Miami (OH) Conservancy District published first
reliable rainfall frequency map for eastern USA 1935: Yarnell’s USDA Rainfall Frequency Data published 1940’s: Research by Bureau of Public Roads – frequency
based sizing 1949: John’s Hopkins University Story Drainage Research
Project endorsed Rational Method 1953: Izzard – Bureau of Public Roads – widely used 1954: SCS Curve Number Method 1960’s: USGS and others begin to develop regional
flood-frequency by regression rather than graphical methods
Standard of Practice in 1962 (Chow) Reviewed 102 empirical and semi-empirical formulas
• 12 Waterway area formulas a(sq ft) = C f(A) • 30 Simple flood formulas
Q = f(Drainage Area) select desired velocity and compute flow area from continuity a(sq ft) = Q/V
• 24 Rainfall intensity formulas Q = CIA • 5 Frequency formulas Q = a + bf(T) • 31 Elaborate discharge formulas
Standard of Practice 1962 (Chow) Talbot Rational Other Dun BPR USGS Historical
AlabamaArizonaArkansasCaliforniaColoradoConnecticutDelawareFloridaGeogriaIdahoIllinoisIndianaIowaKansasKentuckyLouisianaMaineMarylandMassachusettsMichiganMinnesotaMississippiMissouriMontanaNebraskaNevadaNew HampshireNew JerseyNew MexicoNew YorkNorth CarolinaNorth DakotaOhioOklahomaOregonPennsylvaniaRhode IslandSouth CarolinaSouth DakotaTenesseeTexasUtahVermontVirginiaWashingtonWest VirginiaWisconsinWyoming
Formula Table or ChartBurkli-Ziegler
State's Own
State's Own
MN:
•BPR •Rational
WI: •Other •Rational
Independent5 10 15 20 25 30 35 40 50 100 Historical Investigation
AlabamaArizonaArkansasCaliforniaColoradoConnecticutDelawareFlorida +GeogriaIdahoIllinoisIndianaIowaKansasKentuckyLouisianaMaineMarylandMassachusettsMichiganMinnesotaMississippiMissouriMontanaNebraskaNevadaNew HampshireNew JerseyNew MexicoNew YorkNorth CarolinaNorth DakotaOhioOklahomaOregonPennsylvaniaRhode IslandSouth CarolinaSouth DakotaTenesseeTexasUtahVermontVirginiaWashingtonWest VirginiaWisconsinWyoming
Return FrequencyStandard of Practice 1962 (Chow)
“Secondary Highways”
MN = 25 yr
WI = 50 yr
Most Common = 25 yr
Existing Standard of Practice
• “Frequency-based” discharge
• Clear water hydraulics
USGS Regression Equations • Note assumptions – independent of land use • Note methods – dependant upon where applied • Lake / storage distribution not considered • Note error / confidence limits!!
Frequency Curve for Manitou River at Timber CrossingBased Upon Regression Equations
USGS Report 97-4249
0200400600800100012001400
110100
Exceedence Probability (%)
Disc
harg
e (c
fs)
90% Confidence Limits 500 cfs to
1,400 cfs
Equal Probability of Being “Right”
Equal Probability of Being “Right”
NRCS Curve-Number Method • Rainfall Distribution matters!!!
– A Q10-yr Type II can be larger than a Q100-yr Type I – Note assumptions if using a single-event model
• Time / season matters (especially important for ecohydraualics) – plowed field in April ≠ corn field in August
• Antecedent Moisture Content????
NRCS Curve Number “The sample variability in CN can
be due to infiltration, evapotranspiration, soil moisture, lag time, rainfall intensity, temperature, etc. Antecedent moisture condition (AMC) was used to represent this variability. The AMC I is the lower enveloping CN, AMCII is the median CN, and AMCIII is the upper developing CN (Mockus 1964)”
Source: Rallison, Robert and Miller, N. “Past, present, and future SCS runoff procedure”. Rainfall-Runoff Relationship - Edited by V.P. Singh, Water Resources Publications, 1982.
How has the Existing Standard of Practice Performed?
• Has it provided the protection “promised” in our social contract?
• Are there unanticipated effects of using this standard of practice?
Road infrastructure that passes water from
a stream Stream infrastructure that passes vehicles
What is a Culvert Crossing??
Streams Are Complex Systems
Water/ Ice
Bugs
Vegetation
Sediment Mussels Beaver
Fish
Wood
Trees / Roots
Healthy Natural Systems Are Continually Under Construction
Process of Demolition and Reconstruction is Inherent - Vegetation - Streambanks
Change can be either gradual or due to a sudden disturbance
We Have to Remember That Fluvial Processes Are Within the Context of
Natural Disturbance Dynamics
Traditional Clear Water Hydraulic Culvert Design Assumptions w/
Riverine Structures Typically Include • No change over time in:
– Hydraulics – Hydrology – Sediment Supply
• No disturbances / debris • Functional design event
What is Failure??? • Does it mean never washing out or being
over-topped • What about other services such as aquatic
organism passage? • Ability to safely convey vehicles during
“design events” even if overtopped
Consequences of Crossing “Failures” are Profound
• Human Life • Economic • Ecological • Political / Opportunity
Mpls Tribune 6-05
Why Do Crossings Fail?
• Water
Why Do Crossings Fail?
• Sediment
Why Do Crossings Fail? • Ice
Why Do Crossings Fail?
• Debris
Why Do Crossings Fail?
• Beaver
Why Do Crossings Fail? • Frost Heave (smaller pipes)
Traditional Clear Water Hydraulic Culvert Design Does Not Do a Good Job
Considering What Else is in the Stream…..
Revised Design Method is a Hybrid • Considers Performance at Low Flow as
Well as During the “Design Event”
• Physical Analysis – Understand the specifics of the setting the
crossing is being placed
• Frequency Analysis – Manage the risk / transportation system
Fish Passage in One Slide
Pass through what is swimming at you If can get up to the culvert If can get down to the culvert Then it should get through the culvert
• The culvert should not be the limiting factor,
so mimic the existing condition (depth / velocity, boundary conditions, no physical barriers, etc.)
Pass through what is coming at you Accomplished through correct culvert:
• Elevation • Slope • Width • Effective width (alignment and free area) • Area • Substrate / roughness
Sediment Transport in One Slide
Pass through what is coming at you Clear Span Width…Width…..Width Alignment Height
Woody Debris Passage in One Slide
• I don’t know • Maintenance issue - steam the smaller ones • Put in some flood plain culverts – they’re
relatively cheap and should help (though need to document)
Ice Accumulation in One Slide
• I don’t know • Maintenance issue • Trap them • Large enough crossing may be sufficient • Floodplain culverts offer some more protection • I am personally not a fan of Clemson levelers • Why do some beaver build above the crossing?
Beaver Accommodation in One Slide
I don’t know Maintenance issue Perhaps more of a subpavement issue?
Frost Heave in One Slide
Important to Document, Fully Understand, and Communicate the Specific Project
Performance Criteria
• Quantification of Risk
• Allows Evaluation
• Accountability
• Manages Liability
• Reconcile Competing Objectives
First Step in Crossing Design is Often Ignored
IS THE CROSSING NEEDED??
• Really – can other crossings be used, etc.? • Does it need to be permanent – can it be
pulled when done (such as a timber sale)? • Can the transportation system be designed to
minimize crossings?
Some Quick Thoughts About Floodplain Culverts
• Increase conveyance capacity • Benefit for beaver management??? (stay tuned) • Emergency capacity if main is plugged / frozen • Can maintain some better flowlines
– Don’t concentrate flow (velocity) in channel – Retain energy flow in floodplains – Potentially reduce ineffective flow area
• Evaluate – especially valuable where large floodplain conveyance
Schematic of Flowlines Prior to Crossing
1
1
1
2
Single Crossing w/o Floodplain Culverts
Incorporating Floodplain Culverts
Examples of Installed Floodplain Culverts
Inventory found 10-15% of the culverts were undersized and fish passage barriers Additional 20+ crossings not shown
The SNF Has Been Replacing Culverts
Tait River
1935 - Bridge (19’span)
The SNF Has Been Replacing Culverts
Bridge (19’span)
Culvert (12’ span)
Tait River, 1955
Tait River, 2001
Bridge (24’span)
Bridge (19’span)
Culvert (12’ span)
Summary • Streams are complex and dynamic and we
need to recognize the role of: – Sediment -- Wood – Ice -- Beaver – Disturbance dynamics
• The public is demanding a continuation of environmental services….. – fancy way of saying that we need to minimize impacts
on the environment – including accommodating fish passage and allow wood in stream
Summary • Standard of practice evolves over time –
and the present standard is relatively young.
• Clear water hydraulic design alone does not adequately protect the public safety and has unacceptable environmental impacts
• Simply looking at the existing channel (physically-based) does not adequately evaluate extreme conditions – need to quantify risk management
Summary As the body of research work and experience increases, it will be increasingly difficult to justify clear water flood hydraulic design alone as the standard of practice. This will likely impact liability exposure of designers and owners alike with failures / damages during flood events and long term ecological impacts.
Summary Using a hybrid design that includes “channel simulation” and flood hydraulic analysis provides protection to the public that is consistent with the social contract of assumed risk and increased ecological performance We need to ensure we adequately communicate the risks and assumptions made through the development of specific project performance criteria
Questions and Discussion
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