Transcript GIS for storm water management - The Institution of Engineers (India)

INTRODUCTION
Sustainable Urban Drainage depends on
Policy, planning and implementation.
DEVELOPMENT POLICY – Low social
and environmental Impact.
Planning- master plan to conform to
proposed development.
Implementation – construction and
maintenance of Infrastructure
Disasters due to faulty policy & planning
and also due to faulty implementation and
maintenance
Disasters could be Manmade: (i) Change
of land use criteria, encroachment of water
bodies and natural drains and storm water
drains. (ii) Climate Change: Extreme
changes in intensity duration and
frequency of rainfall.
We always blame the climate change !!!
Objective of this paper is to list the current
issues to be addressed and suggest an
approach for sustainable urban drainage
using new technologies.
ISSUES
In India, separate storm water drains/
sewers are in vogue. In practice both
storm water and sewage are mixed.
Changed land use due to increased
urbanization
leads
to
increased
impervious
areas,
reduce
natural
groundwater recharge and results in
higher run off
Drains and water bodies are encroachedSewage garbage and construction debris
are dumped and cannot retain rain water.
.
STATUS OF FEW CITIES
HYDERABAD:
Recent very heavy rainfall has resulted in
inundation of several low-lying areas and
cellars of apartments and commercial
complexes which were several meters
below road level submerging several
cars, two wheelers and diesel generating
sets.
The stagnant water has not receded in
the inundated areas even after the rains
stopped.
Hyderabad

Approach to the residents from flooded
apartments was cut off for several days.
Dewatering of the cellars was done for
several days using fire tenders and pumps.
Rain water collected on streets was not
finding its way to the drains which caused
flooding of streets and damaged several
roads, caused stoppage of traffic or slow
traffic movement.
HYDERABAD AND BENGALURU:
Hyderabad once had 7000 lakes which
has reduced now to about 70 lakes.
(Deccan Chronicle dated 28 December
2016) due to encroachments by
residential colonies and commercial
complexes.
Bengaluru, like Hyderabad, was once a
city of lakes. Out of 105 lakes surveyed in
Bengaluru City,
Hyderabad and Bengaluru
It is found that only four seemed to be in a
good condition while 25 lakes were in a
very bad state.
 98% of the lakes were encroached, 90% of
the lakes were sewage-fed due to
sustained flow of untreated sewage and
industrial effluents, dumping of solid
wastes and building debris. (A study by
IISc on the city's water bodies
COASTAL CITIES LIKE CHENNAI:
Three Rivers flowing through Chennai
collect the storm water from drains and
join the sea (Bay of Bengal).
Increase in intensity of rainfall and for 100
years flood caused heavy damage.
What happens for 100 year floods??
There is no free outfall for disposal of
storm
flows
from
drains
to
channels/rivers) during floods in rivers
and more so during high tide. This results
in backflow and flooding.
Widening of these channels is not
possible due to settlements along the
channels and hence they cannot carry
increased flows due to peak rainfall
intensities.
Rain water during peak intensities will
result in stagnation for in some pockets if
the intensity is more than the design one,
for which mitigation measures are
required.
RIVERSIDE CITIES:
Rivers are normally provided with flood
banks to prevent flood water from
inundating adjoining areas. However
where slopes are flat this creates
problems.
Rain water cannot be fed into rivers by
gravity when rivers are in floods and
needs to be pumped.
ESTIMATION OF STORM FLOW:
CPHEEO manual on Sewerage has
provided guidelines for estimation of
storm Run off depending on intensity and
duration and frequency of rainfall.
The frequency of storm for which the
sewers are to be designed depends on
the importance of the area to be drained.
Peripheral areas twice a year, Central
areas once a year.
In Indian conditions, intensity of rainfall
adopted in design is usually in the range
of 12mm/hr to 20mm/hr.
Suggestions:
Impervious surfaces are not to be directly
connected to streams but to retention
tanks, it results in slow controlled
disposal. Existing Water bodies like
Cascading lakes/ponds could result in
such slow disposal.
New Storm water retention tanks can be
created to retain flood water which can be
released slowly based on river levels.
Could be used for recreation, drinking
and recharging depleted groundwater
Porous Pavements
Cities may not be able to reduce their
'concrete footprint', which prevents
groundwater from entering the soil.
 Porous pavements can be formed with
“No fines concrete” which permits high
flow rate of water.
Captured rainwater can percolate into
ground and recharge the falling down
ground water table
Maintenance of Porous Pavements

To prevent reduction in permeability,
porous concrete needs to be cleaned
regularly. Cleaning can be accomplished
through wetting the surface of the
concrete and vacuum sweeping.
Porous beds of SWD
Wherever soils are permeable, Bed of
SWD will be provided with porous blocks
and also with rain water harvesting pits at
regular intervals. The rain water from roof
tops will enter the street drain directly.
 The storm water from streets will enter
the drain through a silt trap, provided
required camber is provided for the
roads.

SWALES
Outfall to natural drains/water bodies van
be provided with Swales. Grassed swale
is a graded and engineered landscape
feature appearing as an open channel.
The swale is vegetated with erosion
resistant plants which
promotes the
conveyance of storm water at a slower,
controlled rate. Storm water is further
slowed by placement of check dams.
Swales
Check dams on Swales
Monitoring
Monitoring Efficient maintenance of the
drainage network prevention of dumping
of solid waste / entry of sewage into
drains, safeguarding right of way etc,
prevent
Land-Use
Violation
and
encroachment of water bodies along with
their inlets and outlets.
Risk Mitigation and Resilience
Risk mitigation measures for disaster risk
reduction and climate change adaption
are to be built into planning to prevent
impact of disasters due to urban flooding.
There is a need to assess the city’s
resilience in adapting to the disasters by
frequently verifying the preparedness of
risk mitigation teams.
NEW TECHNOLOGIES
Several Kilometers of drains which can
cause flooding when blocked can be
monitored by ultrasonic scans and use
robots to clean the drains
Solar powered cameras can be installed
at strategic locations to monitor water
levels, to transmit to control room for
required action
Extra flood water can be diverted to farm
lands
SUSTAINABLE
SYSTEMS
URBAN
DRAINAGE
(SUDS)
When surface water is controlled, it
becomes a solution instead of a problem
Proper planning for storm water
harvesting will enable local flood control
and contribute to urban greening
Zero Strom water Discharge can be
achieved by landscaped rain gardens/
Vegetative SuDS even in the middle of a
commercial development or more dense
building sites through national or local
planning policies.
Green infrastructure fields can be created
with low impact development (LID) to
achieve greater environmental benefits at
reduced costs.
Congested urban spaces are often the
most challenging situations- phasing of
works to manage the costs.
GIS for storm water management
GIS centric solutions can be used to
manage, coordinate and analyse the
assets and work activities to maintain
reliable and sustainable Storm water
infrastructure.
Asset management division shall work to
add and update the assets.
GIS
GIS can be used to summarise the asset
work/management history such as
number of inlets or length of drains
cleaned as well as inspection and
maintenance frequency for structural best
management practices (BMP)
 GIS
Could also keep record of
photographs, statutory violations and
enforcement actions etc.

O&M
The storm water facilities built by relevant
authorities need to be maintained to
ensure their uninterrupted services.
Efficient maintenance of the drainage
network requires regular upkeep of the
drains through de-silting of drains and
channels, prevention of dumping of solid
waste/entry of sewage into drains,
safeguarding right of way etc.
FLOOD FORECASTING, RISK
MITIGATION AND WARNING
Anna University is supporting Chennai
corporation to design a real time
Computerised flood Model for Storm
water flood forecasting.
Instrumentation has to be installed to
monitor real-time rainfall, stream/river
water levels, and communicate the data
to the server,
Model will identify and give advance
warning about the areas and duration and
extent of flooding/stagnation.
CAPACITY BUILDING
Continuous capacity building will be
required for civic staff:
(i) in estimating effects of climate change
with respect to increase in flash flood
events,
(ii) to improve metrological data collection
and data dissemination
(iii)In flood forecasting methods and
identifying the expected communities
which will be affected.
(iv)In GIS based asset management
CONCLUSIONS
SUD Plan shall meet the challenges posed by
Climate Change adaptable and have flexibility
Adopt latest technologies to design,
implement and maintain the Storm water
infrastructure
A flood control authority/ agency be
constituted for monitoring/ managing Urban
Drainage
Conclusions
GIS based asset management can be used
to Monitor and build up records/
photographs on Land-Use Violation and
encroachments of storm water drains
and water bodies.
 A real time Computerised flood Model
can be built and used for Storm water
flood forecasting in urban areas.

THANKS