Decision support experiments and evaluations using seasonal to ...

For example, observed global sea-level rise was
~1.8 millimeters (~0.07 inch) per year from 1961
to 2003, whereas from 1993 to 2003 the rate of
sea-level rise was ~3.1 millimeters (~0.12 inch)
per year (IPCC, 2007). The Intergovernmental
Panel on climate Change (IPCC) projections
for the twenty-first century (IPCC, 2007) are
for an “increased incidence of extreme high
sea level” which they define as the highest one
percent of hourly values of observed sea level
at a station for a given reference period. The
New York City Department of Environmental
Protection (NYCDEP) is one example of an urban
agency that is adapting strategic and capital
planning to take into account the potential effects
of climate change—sea-level rise, higher
temperature, increases in extreme events, and
changing precipitation patterns—on the city’s
water systems. NYCDEP, in partnership with
local universities and private sector consultants,
is evaluating climate change projections, impacts,
indicators, and adaptation and mitigation
strategies to support agency decision making
(Rosenzweig et al., 2007).
Implementation/Application
In New York City (NYC), as in many coastal
urban areas, many of the wastewater treatment
plants are at elevations of 2 to 6 meters
above present sea level and thus within the
range of current surges for tropical storms
and hurricanes and extra-tropical cyclones (or
“Nor’easters”) (Rosenzweig and Solecki, 2001;
Jacobs, 2001). Like many U.S. cities along the
northern Atlantic Coast, NYC’s vulnerability to
storm surges is predominantly from Nor’easters
that occur largely between late November and
March, and tropical storms and hurricanes
that typically strike between July and October.
Based on global warming-induced sea-level
rise inferred from IPCC studies, the recurrence
interval for the 100-year storm flood (probability
of occurring in any given year = 1/100)
may decrease to 60 years or, under extreme
changes, a recurrence interval as little as four
years (Rosenzweig and Solecki, 2001; Jacobs
et al., 2007).
Increased incidence of high sea levels and heavy
rains can cause sewer back-ups and water treatment
plant overflows. Planners have identified
activities to address current and future concerns
such as using sea-level rise forecasts as inputs to
Decision-Support Experiments and Evaluations using Seasonal to
Interannual Forecasts and Observational Data: A Focus on Water Resources
storm surge and elevation models to anticipate
the impact of flooding on NYC coastal water resource-related
facilities. Other concerns include
potential water quality impairment from heavy
rains that can increase pathogen levels and
turbidity with the possible effects magnified
by “first-flush” storms: heavy rains after weeks
of dry weather. NYC water supply reservoirs
have not been designed for rapid releases and
any changes to operations to limit downstream
damage through flood control measures will
reduce water supply. In addition, adding filtration
capacity to the water supply system would
be a significant challenge.
Planners in NYC have begun to consider these
issues by defining risks through probabilistic
climate scenarios, and categorizing potential
adaptations as related to (1) operations/management;
(2) infrastructure; and (3) policy
(Rosenzweig et al., 2007). The NYCDEP is
examining the feasibility of relocating critical
control systems to higher floors/ground in lowlying
buildings, building protective flood walls,
modifying design criteria to reflect changing
hydrologic processes, and reconfiguring outfalls
to prevent sediment build-up and surging.
Significant strategic decisions and capital
investments for NYC water management will
continue to be challenged by questions such as:
How does the city utilize projections in ways
that are robust to uncertainties? And, when
designing infrastructure in the face of future
uncertainty, how can these planners make
infrastructure more robust and adaptable to
changing climate, regulatory mandates, zoning,
and population distribution?
Lessons Learned
When trends and observations clearly point to
increasing risks, decision makers need to build
support for adaptive action despite inherent
uncertainties. The extent and effectiveness of
adaptive measures will depend on building
awareness of these issues among decision makers,
fostering processes of interagency interaction
and collaboration, and developing common
standards (Zimmerman and Cusker, 2001).
New plans for regional capital improvements
can be designed to include measures that will
reduce vulnerability to the adverse effects of
sea-level rise. Wherever plans are underway for
When trends
and observations
clearly point to
increasing risks,
decision makers
need to build
support for
adaptive action
despite inherent
uncertainties.
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