3. Why we need to manage storm water
• Because impervious surfaces do not allow rain to infiltrate into the ground, more
runoff is generated than in the undeveloped condition. Due to this reduction of
level of water table advances and depletion of ground water resource occurs which
is a key factor to severe drought and scarcity conditions .
4. • To avoid flooding in transportation corridors and
to control damage to properties
• Both cases can cause severe damages and
contamination of the environment if sanitation facilities
are flooded. This results in high costs and notably
massive suffering for the local communities.
5.
6. He divided special tropical rainfall into the following four classes:
(i) Negligible falls: All rainfalls under 12 mm a day unless continuous for several
days; also rainfalls 12 to 40 mm a day, when there is no rain. (ii) Light falls: All
rainfalls up to 25 mm a day followed by similar or heavier falls. Steady pours of 25
to 40 mm a day, when there is no rain of similar or greater amount before or after
that. (iii) Medium falls: Rainfalls from 25 to 40 mm a day when preceded or
followed by any but light falls. (iv) Heavy Falls: (a) All rainfalls over 75 mm a day
or continuous falls at 50 mm a day. (b) All rainfalls of an intensity of 50 mm or more
per hour.
Average rainfall
for 3 months has
been recorded as
916.3 mm
8. Total area of VIT is 370 acres, in which urban spread occupies an area of 220 aces.
Discharge for concrete floors :-
Runoff coefficient[k]=0.85 Avg rainfall i
Area = 140 acres = 54 hectres
average rainfall = 0.00042 m
QP=1/36*K*PC*A
Q = 1/36 * 0.85 * 54 * 10000 * 0.00042
= 5.355 cub.m
= 5355 litre/hr
= 1,15,66,800litre/3 months
This is the discharge for normal rainfall.
9. Dicharge for a peak rainfall , i.e all time record per day = 170.9 mm
Q = 1/36 * 0.85 * 0.007 * 56
= 89.25 cub.m/hr
= 89250 litre/hr
= 192780000 litre/3 months
Dicharge for area including grassland and woodland forests :-
According to the type of soil present in vellore the Runoff coefficient is
taken as [k] = 0.1
Area = 150 acres = 60 hectre
Q = 1/36 * 0.1 * 60 * 10000 * 0.00042
= 0.7 cub.m
= 700 litre/hr
= 1512000 litre/3 months {Discharge for normal rainfall}
13. Infiltration trenches are shallow excavations that are filled with uniformly crushed stone
(similar to soak pits) to create underground reservoirs for stormwater runoff. The runoff gradually
exfiltrates through the bottom of the trench into the subsoil and eventually into the water table.
• As the percolation of water depends on the soil conditions also some time some soils are
not porous in that case infiltration trenches can be used
15. Pervious paths
Pervious pavement is a permeable
pavement surface with a stone reservoir
underneath. The reservoir temporarily
stores surface runoff before infiltrating it
into the subsoil or sub‐surface drainage
and in the process improves the water
quality. Porous materials such as ancient
lime mortars and pervious pavements are
made using relatively mono graded
materials. In the case of pervious
pavement this translates as a lack of
"fine" materials. Pervious pavement is
also sometimes also referred to as “no
fines concrete”
16. Places Where the runflow is more then storage vault
systems are adopted .
The water settles in a tank and are infiltrated through
the gravel and geotextile sheets.
17. • Perforated pipes use a combination of pipe storage and gravel storage to provide detention and
promote infiltration.
19. Blue roofs, also known as controlled flow roof drain systems, provide
temporary ponding on a rooftop surface and slowly release the ponded water
through roof drains.
Blue roofs have weirs at the roof drain inlets to restrict flow.
20. Green roofs consist of a vegetative layer that grows in a specially-designed
soil that may sit above a drainage layer.
Green roofs detain stormwater in the void space of the soil media and retain
stormwater through vegetative uptake and evapotranspiration.
21.
22. Weirs with predetermined flow rates at various ponding depths control
the release rate from a controlled flow roof drain
23. Gutters
Gutters are channels fixed to the edges of roof all around to collect and transport the rainwater from the
roof to the storage tank. Gutters can be prepared in rectangular shapes and semi-circular
Strom drains
24. TREATMENT OF STORM
WATER
Contaminants in water may include algae, air pollution, bird excrement, and
leaves, sand, and dust. Local wells have dealt with these problems for decades.
Installation of filtration and purification equipment can remove these
contaminants at home as well.
First, take measures to keep foreign matter out of the incoming rainwater,flush
devices, gutter screens and other screening mechanisms keep the rainwater as
clean as possible before it enters the conveyance system.
Using screens and filters will greatly reduce maintenance and lengthen the life
of the pump and filtration/purification system.
25. One of the more expensive but effective purification treatments for rainwater is
that of a combination of filtration and UV treatment.
Physical filters “remove particulates, and the UV-light chamber…kills bacteria
and other organisms by exposing them to high-energy ultraviolet light.”
These systems are expensive to install, but also cost quite a bit annually. The
UV light stays on all year, so electricity costs are, relatively, quite high.
26.
27. People commonly use household bleach for this process, which is of concern to
some due to the chemical factor.
wind up boiling the water first, then adding several drops of chlorines into a quart
of rainwater.
you should “allow at least 30 minutes for the chlorine to disinfect your water if the
water is 70 degrees F or above.
Allow up to an hour if the water is near freezing.
28.
29. This is one of the more labor-intensive purification processes, but it also winds
up being a bit more natural in leveraging the sun for purification.
A one-quart Ziploc bag be filled with water, and that the bag be placed on two
feet of aluminum foil, shiny side up in a very sunny place.
The bag needs to heat for several hours and the water should remain at 160F or
higher for at least that long so that waterborne pathogens can be successfully
eliminated.
30.
31. A treatment-train approach to stormwater management involves a range of
measures (primary, secondary, and tertiary) that work together to enhance water
quality.
Primary treatment
The aim is to remove gross pollutants and coarse
sediment (>5mm in size) and help in the downstream treatment of smaller
pollutants.
Secondary treatment
These measures aim to remove fine particles,
sedimentation, and attached pollutants.
Tertiary treatment
Third-stage treatment measures remove very
fine/colloidal particulates, dissolved nutrients, and heavy metals.
