URWH at various scales

Training programme on

Mainstreaming Sustainable Urban Water Management

March 23- 26, 2015

Structure of Presentation

• Surface runoff/ flood management practices to ensure runoff quantity and quality

through public open spaces. • Urban rain water harvesting at institutional/building scale- case example – Birkha

Bawri

• Potential green space for different land use areas • Characteristics of required drainage system according to land use • Integration of different drainage structures for Surface runoff/ flood management

– swale, bioretention , detention ponds and ponds • Reduction in overall Runoff Coefficient and increase in retention for an urban area

(Example Dwarka, Delhi) by using existing open spaces at three different scales:

a) Palam drain catchment level b) Neighborhood level- sector 23 c) Potential area for regional flood water harnessing

Conventional Drainage

Precipitation: Rainfall

Rapid conveyance of water & pollutants

watercourses

Why are efficient drainage system needed?

Hydrograph:

Floods occur quicker due to reduced infiltration

Peak discharge becomes larger

Time

Dis

char

ge

• Attenuate flow

• Promote infiltration & groundwater recharge

Surface /flood management practices

Manage the flooding and pollution aspects of drainage and ensure that the community and ecology are considered in the design. These peactices deliver efficiently and effectively across four key criteria: —

Quantity Quality Amenity Biodiversity

Efficient drainage systems - Surface /flood

management practices

A water sensitive house A water sensitive sector

A water sensitive city

Efficient drainage systems - Surface /flood management practices

at different scales

The Birkha Bawari is designed as a monumental rainwater harvesting structure in Umaid Heritage Township which is based on the concept of both ‘Kunds’ and ‘baoli’ (also referred as ‘bawari’) which were the traditional practice of rainwater harvesting in Rajasthan and Gujarat

Birkha Bawari: Objective

Implementation: Birkha Bawari- RWH structure , is the part of Umaid Heritage- Housing complex and is implemented as the part of township by the same developer. The structure is designed by Architect Anu Mridul .

Location Map of Umaid Heritage in Jodhpur, Rajasthan

Location

The site is located in the city of Jodhpur where the traditional water management system is getting gradually destroyed due to modernisation and urbanisation.

PARAMETERS DETAILS OF THE RWH

SYSTEM

Total catchment area 110 Acres

Green area irrigated 15 Acres

Capacity of RWH structure

(bawari – the storage tank)

17.5 million liters

Volume of rainwater harvested Approx 21.1 million liters

per annum

Cost of System ( in Rs) 80 million

Savings per annum 2.36 million per annum

Year of RWH system implemented 2010

Salient features

Conveyance system

Inlet for road side drainage

Open channels; grated underground storm water drains connecting roof tops

•The rainwater is collected from rooftop and road channels through storm water drains; open channels and slots. •The runoff from the phase-II is collected from the storm drains and connected to the drains in phase-I sloping towards the RWH structure - Birkha Bawari, located in Phase I of the complex.

Parameters Specification

Length 135m

Width 10.5 m

Average Depth 11m (bgl)

Maximum Depth 18 m (bgl)

Average Water Depth 7m

Wall Thickness 0.7 m

Design specifications

17.5 million liters of water from the Bawari is used for landscaping. The same water load is reduced from the other water supply of the region. Birkha Bawari enables a savings of up to Rs 2.36 Million annually for the residents of Umaid Heritage.

Tanks: thus by using the alternate source of water about Rs. 2.36 Million are saved annually.

+ Reduced load on municipal storm water infrastructure.

+ Increase in value of Property

+ Aesthetic Value

Benefits of the project executed

• The housing, Umaid Heritage has around 20% of green area, where the stored water is used for watering the landscaped area of the housing complex.

“The housing colony promises green areas and

cleanliness with traditional water harvesting

monumental structure which clears off the

water from the roads and makes us the proud

resident of the society”- Kamla Jain, Resident

+ Knowledge Dissemination + Recreational Activities

“The beautiful monumental Bawari is one of

the feature of the housing giving the royal

ambiance and serves the environment which

adds to the property value of the plots and

flats”- Ajay Mathur, Marketing manager and

resident

Benefits of the project executed

Surface /flood management practices in

public open space

Public open space for such practices are characterized by being located within green space or other clearly defined public areas that can manage the storage and conveyance of surface water runoff. Depending on the design and characteristics of the site there will be a convenient location where the intermediate source control area becomes part of accessible public open space.

Filter strips

Swales

Bioretention areas and raingardens

Detention basins

Integrating different Surface /flood

management practices options

Filter strip swale Porous paving

Porous paving

eg reinforced grass or gravel surfaces, porous concrete and porous asphalt

How would these practices cater the quantity of storm water

How would these practices handle the quality of storm water

•Wildlife habitats •Land-values •Recreation opportunities

How can these provide Amenity value •Educational opportunities

•Increase in time of concentration

•Runoff Volume- decrease

•Peak Discharge- Reduce

•Sedimentation •Filtration

•Heavy Metals

•Aesthetic & Ecological quality of the landscape

Swale

Swale is densely vegetated trapezoidal or triangular channels with low pitched side slopes designed to convey runoff slowly

•Used to capture, direct and infiltrate rainwater into the soil •Alternate to curb and gutter system

Swale

Swale example

Swale design-Design Criteria

Location

•Next to roads •Landscape areas •Adjacent to car parks

Landscape areas

Land Uses

•Residential, commercial, or institutional development conditions •Residential uses -densities of 4 dwelling units per acre. •Large commercial site applications - may require multiple channels according to sub catchments

•Highway or low- and medium-density residential road runoff, (adequate ROW) •Other suitable areas- sports fields, golf courses, and other turf-intensive land uses

Swale design-Design Criteria

Soil Requirements

Vegetation

It should not be constructed in gravelly and coarse sandy soils (cannot support vegetation). Thumb Rule 1: Soil infiltration rate > 0.2 mm/s (avoid compaction of the soil)

Fine, close –growing, water resistant grass (more the surface area of the vegetation exposed to runoff more the effectiveness of the system). Examples: Reed canary grass, grass-legume mixtures, and red fescue.

Geometry

Shape: Trapezoidal cross section Side Slope: 1:3 (recommended to maximize the wetted channel perimeter of the swale)

Thumb Rule : The total surface area of the swale should be 1% of the area that drains to the swale Thumb Rule : for the effectiveness of the swale to treat runoff, depth of the storm water should not exceed the height of the grass.

Longitudnal Slope< 2% if drain tile is incorporated and Slope> 4% can be used if check dams are placed in the channel to reduce flow velocity

Open channel flow, such as in a swale, is based on two formulas

1. Manning’s Equation

2. Continuity Equation

Continuity Equation Flow rate and velocity

q = A V q – flow in cu. ft/s

A – cross-section area for flow, sq, ft

V – flow velocity, ft/s

The flow velocity is maintained at 0.5m/s (Austrailan manual) Maximum flow rate < 140 litres/second (0.14 m3 /s) (EPA manual)

Flows

Manning’s Equation

Velocity of flow in an open channel is given by Manning’s Equation

V = (1.486 R2/3 S1/2) / n

V – flow velocity, ft/s

N – Manning’s roughness coefficient for open channels

R – hydraulic radius, ft

S – channel slope, ft/ft

Type of channel Lining Design n

Grass 0.033

Riprap 0.035

Turf Reinforcement 0.038

Manning’s n values for various channels.

R - Hydraulic Radius

R = cross-section area of flow / wet perimeter Water Surface

Wet Perimeter

20 5

4 1

Area = 20 sq, ft WP = 4 + 5 + 4 = 13 ft R = 20/13 = 1.54 ft

Area = 20 sq, ft WP = 1 + 20 + 1 = 22 ft R = 20/22 = 0.91 ft

Larger R = less resistance to flow

Bio retention basin

It is a planted depression that allows rainwater runoff from impervious urban areas like roofs, driveways, walkways.

•This reduces rain runoff by allowing stormwater to soak into the ground •Rain gardens can cut down on the amount of pollution reaching streams

Bio retention basin

Bio retention

design-Design Criteeria

Location

•Parking lot islands. •Parking lot edge. •Road medians, roundabouts •Right-of-way or commercial setback. •Courtyards. •Individual residential lots. •Unused pervious areas on a site. . •Retrofitting

Land Uses

•Residential, commercial, institutional development

Bio retention

design-Design Criteria

Available Space.

•The bioretention surface area will be approximately 5% to 7% of the contributing drainage are

Land Uses

•Residential •commercial •institutional development

Bioretention areas

Components of bioretention area:

For temporary storage of surface water

Grass filter strip/ grass channel:

To reduce incoming runoff velocities and to filter particulates

Ponding area

Plants

To provide vegetative uptake of pollutants.

Bioretention example

Bioretention Pollutant Removal

University of Maryland

Cumulative

Depth

(ft) Copper Lead Zinc

Phos-

phorus TKN Ammonia Nitrate

1 90 93 87 0 37 54 -97

2 93 99 98 73 60 86 -194

3 93 99 99 81 68 79 23

Field 97 96 95 65 52 92 16

Removal Efficiency (%)

Box Experiments

Dr. Allen Davis, University of Maryland

2’

2” Mulch

Infiltration System

Highly Pervious Soils

Existing Ground

2’

2” Mulch

Drain Pipe

Combination Filtration / Infiltration

Moderately Pervious Soils Gravel

Sandy Organic Soil

Existing Ground

Detention basin

Detention basin example

Ponds

Factors for designing effective Surface /flood

management practices

Approach for

catchment

development

Scope of development

Time of

Concentration-

Increase

Lengthening flow paths and thus reducing the

length of the runoff conventional conveyance

systems.

Runoff Volume-

decrease

Reduce/minimize imperviousness, preserving

more trees and meadows.

Peak Discharge-

Reduce

retention storage for volume and peak control,

natural drainage patterns

Water Quality-

Improve

According to catchment landuses, sand filters,

retention areas

Flooding-

controlled

use of additional runoff, use of flood water in

low lying area

References

Sheet No. 2

Urban Development: planned and executed in a manner so as to lower

the hydrological impact of urbanization and present opportunities for improved water

management

RAINWATER: Availability in area, management to meet water demand in local areas.

STORM WATER: managed through surface water bodies+ optimal storm water channel : Green infrastructure

WASTE WATER: managed and reused for non‐domestic purposes

Storm water and resource management- case study Dwarka

Steps for analysing catchment areas

a) Delineation of Catchment area b) Calculation of runoff discharge

c) Identifying potential

sustainable strategy

Preparation of suitable sustainable

urban drainage system strategies

landuses Runoff coefficient

Commercial

(80% Impervious)

0.7

public-semi public

(70% impervious)

0.6

Park 0.3

References

Landscape architecture time saver standard by Charles w. Hanis and Nicholas Tines

Trunk drains Discharge

Capacity Area

Cumecs

(%)

Increase in

discharge

TD5

18.26 Cusec 27 485 67.80 151.10

TD4

10.98 Cusec 14 324 48.58 247.03

Scale: 1:300

0

6

12

24 KM

Sheet No. 6

Watershed analysis

Table: calculation of discharge for each of catchment area of drain for 25 year peak hour rainfall.

Storm water and resource management- case study Dwarka

Catchment analysis

Delineation of Dwarka into different catchments of respective trunk drains

36%

25%

5%

34%

DDA Housing

33%

14% 20%

33%

Institutional

Conventional break up of open areas for

Dwarka, sector 23, Delhi

22%

3%

29%

46%

Group Housing

Built up %

Open vegetative %

Openpaved%

Open lawnarea %

The conventional practice of making the surface paved, leads to loss of opportunity space for rain water harvesting structure and also increase the runoff coefficient. However, the existing lawn/green space can be used to their full potential for designing and planning of rainwater harvesting structure.

References

•Suds Manual. London: 2007. •NRCS Planning and Design manual. Storm Water Management for Industrial Activities. •Simpson, P. (2010). Towards sustainable water stewardship. •Greater Dublin Strategic Drainage Study.

1

2

3

4

5

6

1

1

Along road R 1

Swales

Filter Strip:

R 1

Application of Sustainable strategy for Palam drain watershed area of Dwarka

RWHs in Catchment

area for drain TD-3

Area

(sqm)

Depth

(m)

volume

(Cum)

Bioretention 3299 0.3 989.7

pond 1 1507 0.3 452.1

pond 2 1569 0.3 470.7

swale 47690 0.1 4769

Retention basin 1 1247 0.3 374.1

retention basin 2 1839 0.3 551.7

gully trenches 75059 0.2 15011.8

total area 132210 total 22619.1

Strategies for watershed area with case example of one of the watershed of drain TD-3 (Palam drain)

Area- 8% of public open space of watershed area Volume- 20% of annual rainfall falling in the watershed (113095mm) Thus 5% to 15% area of open space of each catchment area can retain 100% of 1 hour Peak Discharge from watershed for 25 year storm.

Public open space-District park

Storm water and resource management- case study Dwarka

Application of strategy for one of the Catchment area

Palam drain catchment level

If strategies for only reduction of overall runoff coefficient are applied than 22% of reduction in peak discharge achieved. And after that if retention strategies for effective drainage systems applied for 5-10 % of public open space than 100% of exceeding peak discharge is reduced.

Direct precipitation over depression: 1.4 Mcm (6437 mm x 150 Ha x .3 coef) Regional flood: 37 Mcm Evaporation loss = 30% = 1mcm Total water storage capacity : 6Mcm

Use of water: Horticulture Construction works

Typical section through natural reservoir

Potential area in site for flood water harnessing

Outlet gate

Inlet gate

For using the total potential of low lying area of site: By Construction of No. Of ponds to increase the capacity (depth not more than 0.6 m). Construction of inflow and outflow gates with sluice water movement and collection The total water collection by direct precipitation and by no. Of ponds is 6 mcm. This 6 mcm of water shall be used for bulk uses of Dwarka.

Major conclusions (Specific to Dwarka):

Storm water and resource management- case study Dwarka

Potential area for regional flood water harnessing

Overall Runoff coefficient reduction from 0.62 to 0.4