discussion topic

1
discussion topic

• Models that are eco-sensitive ought to be
  encouraged, over those that arent.

2
A model is a concept. Concepts are used in
engnrg design and are improved by experience. We
do not necessarily require the model that most
approaches perfection, rather we seek the model
that provides an acceptably accurate explanation.
Simple models are often said to be better than
complex models. Optimal model complexity depends
on the questions to be resolved and the resources
available.
3
In this presentation there is nothing new under
the sun, Horatio

• 1. We develop an obvious case for eco-ethical
  engineering,
• 2. which clearly implies more complex
  design-analysis models,
• 3. and supports another old philosophy
  period-of-record (continuous) design models

4
Starting suppositions

• World's 1 long-term problem is Loss of habitat
  and bio-diversity, apparently irreversible.
• Environmental problems are caused by humans,
  mainly by their population pressure, and can be
  solved by modifying their behavior.
• On the other hand, we generally replace acute by
  chronic problems, at a price vigilance.

5
And a startling position

• Often, simplistic methods are associated with
  poor drainage design, which is in turn associated
  with tough living conditions, whereas complex
  methods are associated with desirable conditions.
  There may be cogent reasons for this
  relationship, related to society knowledge and
  eco-sensitivity.
• Reversal of environmental degradation has been
  shown in East Africa to lead directly to real
  improvements in living conditions, including
  employment opportunities.

6
An archeology of stormwater design
PERIOD MYTHOLOGY
IMPLEMENTS 1. "ante-diluvian "rational"
formula, slide rule, from c1892
I-D-F curves adding m/c, no data. 2.
ancient" event hydrology
batch mainframes, from c1932 unit
hydrographs, pocket calculator.
design storms. c1970 3. "modern"
continuous modeling 16-bit pcs, from c1962
time series management minis
c1980 4. new more than engineering.
32-bit work stations, from c1993 networks
These four periods correspond to use of a 1.
technique, 2. methodology, 3. philosophy 4.
value system
7
R0
Things should be made as simple as possible, but
not any simpler." - Albert Einstein
R1
8
Traditional design methods use

• Few parameters, that subsume great complexity
• Empirical equations, based on curve fitting
• e.g. linear unit response functions, and
• design storms based on IDF analysis. 
• Reasons for Use
• Tradition,
• thought to produce conservative results,
• thought to be inexpensive and easy to use.
• Real reason circumvents the need for thought,
  eliminates complicated, modern issues.

9
From Pechers doctoral study, Germany ca. 1970
For permeable surfaces, vertical occurs at
capacity of upper layer
10
R81

• Event vs continuous hydrology
• Event hydrology accounts for wet event processes
  only.
• Continuous hydrology on the other hand includes
  all dry weather processes.
• Why do some agencies choose to ignore half the
  processes (the model is provided free, a generous
  gift of the US Govt)?

11
R81

• Event vs continuous hydrology
• Event hydrology is mistakenly thought to be a
  cheap design method it does however produce
  cheap (inadequate) designs. E.g., unit
  hydrograph and design storm methods cannot
  account for ecosystem concerns.
• Continuous hydrology on the other hand allows
  consideration of aquatic ecosystem (and many
  other) issues.

12
Event models generally.

• Do not simulate water quality build-up and
  wash-off
• Do not simulate erosion and fluviology
• Do not simulate important aquatic bio-system
  parameters
• Do not simulate long-term performance
• Do not account for the large number of light
  rainfalls
• Do not account for sequences of high flows
• Do not account for sequences of low flows
• Do not account for seasonality
• Require start-up conditions that are
  inconsistent, highly uncertain and critical
• Deny consideration of ecosystem issues
• Assume everything is stationary
• Etc.

13
An overiding issue is the so-called first flush

• Event models cannot predict first flush effect
• First flush (gt50 TSS in rising limb of the
  hydrograph) probably exists wherever we have
  efficient drainage
• Manufactured treatment devices and other BMPs are
  excellent for capturing the first flush
• We obviously need to concentrate MTDs wherever a
  first flush may be experienced
• Their long-term costs/benefits should be computed
• We therefore need a continuous model that
  correctly predicts first flush.

14
We do not need to immediately and peremptorily
replace established event models

• What I am suggesting is dont replace your
  traditional methods simply encourage addition of
  the (say) 50-years design storm to your current
  slate of design storm computations.

15
Why SWMM?

• Most widely used general stormwater program
• Used extensively for urban watershed planning,
  design, development, management, and regulation.
• Vast archive of applications, users etc
• PCSWMM for Stormceptor integrates and dovetails
  with these area-wide models.

16
How does this concern us?

• Urbanization is by definition involved in habitat
  and biodiversity (HB) degradation (medicine is
  the complement)
• Globally, we are told, HB problems are serious
  and getting worse
• Long-term sustainable civilization, we are also
  told, is dependent on restored HB

17
Some humble suggestions

• Develop in officials a deep eco-ethos to restore
  bio-diversity
• Develop in the landscape intervention community a
  new spirit that restores ecosystem diversity.

18
Design should follow a sacred ecology of
focussing on less-unsustainable ecosystems

• biological equity must determine design,
• design must reflect bio-regionality,
• projects should use renewable energy systems,
• the living world should be the matrix for all
  design, which should integrate living systems,
  and follow the laws of life, and
• projects should heal the planet

19
Good design
R86

• examines very long-term changes and impacts
  (gt100y)
• accepts the limits of our discipline
• corrects the human behavior that caused the
  problem to the ecosystem
• improves restores the natural balances and
  bio-diversity, imitates the structure of the
  natural, native or indigenous system, and is good
  for all parts of the natural system
• does not enrich one individual or group to the
  distress or impoverishment of another
• is in harmony with good character, cultural
  value, and moral law.

20
R81
On simplistic vs meaningful models

• Simplistic short-term models have trapped us in a
  rut of producing only politically-correct
  solutions that fit single-minded ideas of
  economic growth (e.g. what is the minimum-cost
  unit?)
• Complex, long-term and meaningful models open up
  a greater variety of options (e.g. what animals
  are affected by installing the unit?)

21
Prohibit uninformed use of incomprehensible models

• More intelligent use of more credible models is
  what we seek. Training is important.

22
R2
As a rule
Models are used to help select the best among
competing proposals. It is fundamentally
irresponsible and unethical for modelers not to
interpret their inherent uncertainty.
23
The implicit problem in engineering design is
to find the optimum cost-effective array of best
practices. A solution may be stated if the
75-year rainfall time series that occurred at the
International Airport, had in fact occurred at
Foxran Estates, then plan 126 would have been the
most cost-effective of the 329 plans examined -
had they, of course, all existed over this time.
24
Models inevitably become more complex
- model complexity is related to the total number
of uncertain input parameters.
25
R89
Summary

• For design follow a personal or sacred ecology
  (biological equity, design to restore
  bio-diversity, very long-term modelling).
• For design and analysis, eschew simplistic models
  that do not help to restore the planet.
• In development, consider the N American idea of a
  great spirit based on long-term ecosystem health
  and diversity.

26
The end
see you on-line at
www.computationalhydraulics.com
bill_at_computationalhydraulics.com wjames_at_uoguelph.
ca