1-yr (18)

Managing Risk and Economics:
A New Paradigm for Developing
Urban Drainage Projects
Steve Eubanks, PE, CFM, City of Fort Worth
Brenda Gasperich, PE, CFM, Brown & Gay Engineers
Jeff Whanger, PE, CFM, Brown & Gay Engineers
A
How do you compete?
• Challenge the conventional
wisdom
• The numbers do not lie
Challenging the conventional wisdom
• Baseball teams have
traditionally relied upon
scouts who assess players
based upon observations,
biases, and prejudices
• Process never challenged
or validated
• Sort of a “good ol’ boy”
system
• A lot of bad investments
The numbers do not lie
• Sabremetrics – the search for objective knowledge
about baseball
• Coined by Bill James, after Society for American
Baseball Research
• Statistical measures to:
– Question traditional measures of baseball evaluation
– See true value in players (bargains)
– Example: OBP >> AVG
Moneyball Example – 2002 A’s
• After 2001, lost 3 best
players to free agency
• Could not afford to replace
with “all star” players
• Instead, signed 3 players
whose combined OBP
equalled Damon and
Giambi
• 2002
– Won Division
– 20 game winning streak
What does this have to do with flood mitigation?
• You are the Oakland A’s, not the New York Yankees!
– Never enough funding
– Your fans have high expectations
– Must compete with higher profile funding expenditures (traffic,
police, schools)
• Can we take a “sabremetric” approach to flood
mitigation?
• Should we?
• YES!
A
Arlington Heights
Neighorhood
Fort Worth, TX
•
•
•
•
•
100-year old storm sewer
Sumps in streets
Under-capacity
No escape path
Frequent flooding
June 28, 2004 – Central Arlington Heights
Central Arlington Heights
92 homes damaged
during a 100-year
event
Conventional Wisdom
• Projects must provide
100-year capacity
• Calculations must be
based on a 24-hour
rainfall event
• Projects must not
inconvenience the
community
• Projects should not
consider buyouts
The Challenge
In most situations we
must find a bit of
compromise in all
three elements
Let’s think about a rain gage
(properties damaged)
4”
100‐yr (92 )
50‐yr (85)
25‐yr (70)
3”
10‐yr (55)
5‐yr (42)
2”
2‐yr (29)
1‐yr (18)
1”
System
Capacity
1 hour
What if it rains more than 1”?
(properties damaged)
4”
$5.1M
100‐yr (92 )
$4.7M
50‐yr (85)
$4.1M
25‐yr (70)
3”
$3.5M
10‐yr (55)
$3.0M
5‐yr (42)
2”
$2.5M
2‐yr (29)
1‐yr (18)
$1.9M
$5 M
$4 M
$3 M
$2 M
Single Event Damages
$1 M
$0.0 M
1”
System
Capacity
1 hour
Damage X Annual Probability
4”
100‐yr (92)
50‐yr (85)
25‐yr (70)
3”
10‐yr (55)
5‐yr (42)
2”
2‐yr (29)
1‐yr (18)
1”
$1M
$500 K
$250 K
$0 K
Damage X Annual Probability
1 hour
Expected Annual Damage
• Area under the curve equals the expected annual damages ($2.6M)
• Present value of expected annual damages can be computed (Using 50 year cash flow, i=7%) 4”
100‐yr (92)
50‐yr (85)
25‐yr (70)
3”
10‐yr (55)
5‐yr (42)
2”
2‐yr (29)
1‐yr (18)
1”
$1M
$500 K
$250 K
$0 K
Expected Annual Damages
Value = $36.5 million
1 hour
Design Criteria (Conventional Wisdom)
From Current COFW Design
Manual:
The design storm is a
minimum of the 100-year
storm for the combination of
the closed conduit and surface
drainage system.
Expected Annual Damage
4”
Net Present Value = $36.5 million
100‐yr (92)
50‐yr (85)
25‐yr (70)
3”
10‐yr (55)
5‐yr (42)
2”
2‐yr (29)
1‐yr (18)
1”
$1M
$500 K
$250 K
Expected Annual Damages
$0 K
What if we increase
capacity to 2 in/hr???
1 hour
Central Arlington Heights
Proposed Under-Street Detention
Western
Under-Street Detention
Bryce-Hulen
Surface Detention
Ashland
Under-Street Detention
Under-Street Detention
Modeled Flood Reduction
Net Present Value of Damages
4”
• Area Under the Curve equals the expected annual damages if capacity improved from 1”/hour to 2”/hour
100‐yr (92)
50‐yr (85)
25‐yr (70)
3”
10‐yr (55)
5‐yr (42)
2”
2‐yr (29)
1‐yr (18)
1”
$1M
$500 K
$250 K
$0 K
Expected Annual Damages
Existing Damages = $36.5 million
Residual Damages = $7.5 million
Benefit = $29 million
1 hour
Properties at Risk of Flooding
Storm
Existing
Post‐Project
1‐yr
2‐yr
5‐yr
100‐yr
18
29
42
92
10
22
33
92
Properties Removed
8
7
9
0
BCA for Planned Detention Projects
Damages
Cumulative Benefits
Cumulative Cost
Cumulative BCR
Existing Conditions
$ 36,503,254
‐‐
‐‐
‐‐
Ashland Detention
$ 35,220,075 $ 1,283,180
$ 975,000
1.32
$ 32,332,898 $ 4,170,356 $ 3,177,284
1.31
Ashland Detention + Western Detention + $ 30,759,546 $ 5,743,708 $ 4,084,284
Hulen/Bryce Detention
1.41
Ashland Detention + Western Detention
Moneyball approach to flood mitigation
• Challenge conventional wisdom
– Rethink Level of Service
– Rethink your hydrology
• The numbers do not lie
– Technology can assist in developing information over a larger area
– Develop smart metrics
• You can compete with the Yankees!
– Optimize performance
– Find value
The End
Questions?