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Fifty Years of Innovation in Urban Stormwater Management
Jiri Marsalek National Water Research Institute,
Burlington, ON, Canada
Technical University of Lulea, Sweden Lulea, Sweden, Dec. 3, 2013
2
World Population: Urban and Rural Areas (UN, 2009)
Global pop. 3.5 billion
Global pop. 7.4 billion
LD rur
LD urb
MD urb
MD rur
• Swedish population: Total 9.3, urban 7.9 million (85%)(2010, CIA)
3
Urban Drainage: Systems Analysis (SA)
• Problems – unsustainable growth of urban drainage systems (UDS)
• Analytical tools – models • Solutions – BMPs and LID
and similar • Evaluations (including costs)
– mostly by modelling • Implementation –through
master drainage plans, regulations and policies
• Problem definition – evolving, the cycle repeats itself
Problem definition
Development of analytical tools
Problem solutions
Evaluation of solution alternatives
Evaluation of solution alternatives
Implementation
4
Impacts of urbanization: Surface runoff
Envelope
Return period (y)
Time
Runoff Hydrograph after urbanization
Runoff hydrograph
before urbanization
Dis
char
ge
Pos
t-dev
elop
men
t run
off p
eak
/ pre
deve
lopm
ent p
eak
5
Stormwater quality
• Discovery period (mid 1960s – late 1970s), generation of national databases (1980s) (e.g., US NURP (1983))
• Findings: – A general understanding of stormwater quality with respect to
conventionals (TSS, COD, BOD, nutrients), indicator bacteria and some priority pollutants (inorganics – trace metals)
– Occurrence of EPA priority pollutants (inorganics, some trace organics – PAHs, older pesticides) in stormwater
– Producing arguments for continuing research on stormwater pollution and its mitigation by control measures
• Current focus – priority pollutants, particularly under the EC Water Framework (recent pesticides, PCBs, plasticisers, emerging pollutants)
6
Stormwater quality (NURP) Constituent EMCs – median EMCs – 90th percentile
TSS [mg/L] 100 300
BOD5 [mg/L] 9 15
COD [mg/L] 65 140
P tot [mg/L] 0.33 0.70
P diss 0.12 0.21
TKN [mg/L] 1.5 3.3
NO2,3 0.68 1.75
Cu tot [µg/L] 34 93
Zn tot [µg/L] 160 500
Other concerns: Indicator bacteria (EC: 103 – 104/100 mL), PAHs (from traffic), waste heat (impacts cold water fisheries), priority pollutants
7
Tools for solution assessment – models Example: U.S. EPA SWMM runoff simulations
(Burlington, Ontario, 1974)
Measured runoff
Time (h)
Dis
char
ge [m
3 /s]
Rai
nfal
l int
ensi
ty [m
m/h
]
Simulated runoff
8
Impacts of urban runoff on receiving waters
Factors affecting biological communities: flow regime, habitat structure, biotic interactions, food sources, chemical variables (pollution)
Seasonal effects were noted (chloride)
Log (total number/m2) Site
Sediments from all sampling sites
10 most dominant taxons
Num
ber o
f tax
ons
9
Current goals of stormwater management (SWM)
Goals Means of attaining the goals
Control of runoff peaks, preservation of water balance
BMPs, LID, Green Infrastructure, … (control of water balance and runoff )
Protection of stream geomorphology
BMPs & LID (control of runoff flow magnitude and duration)
Protection of water quality BMPs & LID (control of stormwater quality, including source controls)
Maintaining / enhancing biodiversity (ecological functions)
BMPs & LID (mimicking predevelopment water balance and water quality)
Enhancement of beneficial uses of stormwater
BMPs & LID (selected to protect aesthetics, recreational uses and ecological functions, SW use)
10
Solutions: BMPs, LID, Green Infrastructure
• BMPs (best management practices) serve to mitigate urbanization impacts on runoff quantity and quality
• Early BMPs: wet and dry ponds, infiltration trenches and basins, porous pavements, constructed wetlands, sand filters
• LID (low impact development) – a comprehensive, landscape-based approach encompassing strategies to maintain the predevelopment land hydrology and ecology (identical to “Design with nature”, Ian McHarg, 1969)
• Typical LID measures: bioretention, bioswales, green roofs, permeable pavements, box planters, naturalized drainage channels, vegetated filters/strips,
Credit: M. Dietz From Kerr, Wood, Leidal
11
Hydrology of BMPs a LID: Annual water balance
S s
ewer
SW
pon
d
Dr.
ditc
h
Inf.
Tren
ch
Bio
rete
ntio
n
Gre
en R
oof
ETINF
RUNF0
1020
30
40
50
60
70
80
90
100B
alan
ce fr
actio
nFr
actio
n [%
]
Surface runoff
Infiltration Evapotranspiration
12
International Stormwater BMP Database: Performance in removal of TSS
Bioreten-tion
Green roofs
Wet ponds
13
Life-cycle costs of removing 1 kg of TSS by SWM (from Urbonas)
0
2
4
6
8
10
12
14
16
18
sand filer basin wet pond porousconcerete
pavers
porouslamndscape
detention
oil & gritseparator
inlet inserts
Annu
al c
ost o
f rem
ovin
g 1
kg o
f TSS
[$/k
g/y]
14
SWM Implementation
• Understanding of technical-scientific issues of SWM has greatly advanced during the last two decades
• Yet, there is a tendency of promoting “idola fori” (idols of the market) defined by Sir Francis Bacon (1561-1626) as “fallacies arising from the imperfections and the abuse of language”.
• Examples include the thoughts that pavements should be excluded from cities (ignoring their function), all stormwater is a resource (this would include catastrophic rainfalls), etc.
• This needs to be corrected by public education
Source: Wikipedia
Francis Bacon
15
Smart Cities
• There is realization that the city’s performance in meeting end-users needs does not depend just on hard infrastructure, but also on the availability and quality of knowledge communication social infrastructure
• These concepts were introduced into urban planning as “smart”, “intelligent” or “liveable” cities featuring attractive built and natural environments
• It is of interest to note how these concepts are viewed by the economists (The Economist magazine, EM)
• EM asserts that these concepts follow the “hype cycle”, characterized by a period of inflate expectations leading to some lower level of sustained productivity
16
The Hype Cycle (after Gartner)
• A discussion model, but based on past experiences
• The plateau of productivity is hard to predict (but experts try)
• For smart cities, EM expects to see some benefits in late 2013 or in 2014
Visibility
Time
Peak of inflated expectations
Trough of Disillusionment
Plateau of productivity
Technology trigger
17
UDS Innovation • Growing cities create pressure on existing
water systems, solutions require innovation • Past innovation in SWM – adopting /adapting
existing concepts from catchment hydrology and wastewater management (low hanging fruit)
• Uptake of innovation is impaired by technological lock-in (long design life) and monopoly in service delivery
• Near future innovation of sewers, BMPs will proceed slowly (limited incentives)
Source: The Economist
18
Innovation (cont. 1)
• Other aspects involving private enterprise and research – e.g., updating UDS problem definition, software for planning, design and operation, and environmental technologies will keep evolving, because of incentives
• Environmental technologies - proliferation of devices treating SW, but their full (life-cycle) costs including maintenance may be prohibitive - need to be assessed
• A further impediment may be ambiguous terminology - often introduced by vendors of SW equipment wishing to distinguish their products from others already on the market by implying superiority
19
Evolution of UD Problem Definition
• Common understanding of urbanization impacts is fairly advanced, but a number of issues require further research:
– building materials as in-situ pollutants, – priority pollutants, – climate change impacts on UD, and – drainage in special climates
• Building materials – progress has been made, but concerns are continuing (plasticisers and biocides in industrial paints and building materials
• Municipalities have limited control options • Positive effects – e.g. self-cleaning concrete
with embedded TiO2 nanoparticles (may remove pollutants at street level)
20
Priority Pollutants
• Recent studies of priority pollutants were motivated by the EU Water Framework Directive
• Such data are useful for assessing the pathways and fate of priority pollutants, but their control is likely outside of municipal mandate – will be achieved by policy instruments, as done e.g., in the case of lead
• Municipal “ownership” of the PP issue would be costly and require special removal of disposal of contaminated materials (e.g., pond sediment disposal might increase two orders of magnitude)
21
Example of Policy Control Instruments: Phasing Pb out of Gasoline
• Phasing Pb out of gasoline was highly effective
• Highway runoff data indicate reduction of Pb in runoff about 30 times
• This is actual prevention, not just a diversion, or immobilization
• There are other similar opportunities
US Highway Data (1970s)
CDN Highway Data (1990s)
10
1
.01
.001
Pb (mg/L)
Z score-2 -1 0 1 2
Reduction 97%
22
UDS: Climate Change
• Excellent monograph produced under the leadership of IWG on Urban Rainfall • The problem of producing quantitative assessment of
impacts is highly challenging and complicated by the dynamic nature of urban areas
• Global or regional climate model outputs need to be downscaled to few km and resolution in minutes
• Uncertain results depend on the downscaling process, standard procedures need to be developed
• So far, focus on flooding, but the performance of the stormwater management infrastructure in a changing climate should be of interest as well
23
Cold climate issues
• Stormwater management research in cold climate is more challenging than in temperate climate, yet not receiving adequate attention
• Some issues: higher rates of pollutant releases, shock wave pollutant transport (producing toxicity), reduced effectiveness of BMPs
• More research needed
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
10-Jan 24-Jan 07-Feb 21-Feb 07-Mar 21-Mar 04-Apr 18-Apr
Date
Cum
ulat
ive
Mas
s C
hlor
ide
(kg)
Snow storage runoff treatment train
Chloride runoff from snow storage site
24
Some UD Research Challenges
• Models vs. prototypes: While the value of studying processes under controlled conditions is indisputable, most lab studies ignore some important field process conditions, and field proofs are needed (example: boundary conditions in lab studies of porous pavements)
• Site vs. catchment: Vast majority of BMP/LID studies investigates mass balance of single facilities
• Water management goals are much broader – how such measures protect the whole catchment and its resources; what is the minimum uptake of BMPs to achieve these goals?
25
Study Duration
• Much of the BMP/LID research is of short duration, may miss gradual deterioration of performance due to:
– Reduction in percolation rates due to clogging, or biofilm growth – Reduction in sorption sites – Chemical transformation processes – Reduction in treatment volume by sediment accumulation
• Need triggers for maintenance operations, going beyond cost-benefit analysis – including environmental risks
26
Frequency of BMP maintenance
BMP Facility Frequency of maintenance
Large maintenance
Curb inlet screens 2-4 times per month
Cartridge sand filters
2-3 times per year
Hydrodynamic separators
Once a year
Rain gardens Several times per year
Detention ponds 2-3 times per year Sediment removal 10-30 years
27
Measuring SWM Research Accomplishments
• Different criteria, e.g., biological community assessment, return of critical species, or DCIA
• In research, papers proliferating in great numbers (interest in the urban environment, general availability of funding)
• For many papers, it is becoming challenging to identify how they serve the end-users
• The gap between the end users and researchers grew to the point that we need “knowledge translation” providers
• Scientific journal revenue estimated at $6 billion annually, With high profit margins
• The business model is unusual – the valued product (new knowledge) is provided free, the quality control depends on engaging volunteers and competitors
• Changes are occurring in the form of open-access publishing; which depends on paper fees for financing, hence a potential conflict of interest
28
Conclusions
• Remarkable progress in stormwater management has been achieved during the past 50 years,
• Requirements on SWM are changing as a result of: – Dynamic nature of urban areas – Climatic changes (particularly precipitation) – Changing releases of pollutants, and – Changing objectives of UD operation arising from changing
expectations of the urban population
• Thus, demands on innovation and research will continue