Blue Green Solutions

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Blue Green Solutions Guide

The city is comprised of urban components, which 

collectively act to create “Living Environment 

Quality”: an aggregate of all factors (indicators) 

influencing the quality of our living environment. 

The ultimate aim of the BG Systems approach is 

to achieve the highest level of Living Environment 

Quality, at close to optimal cost. This is achieved 

by optimising the interaction between urban 

components, including BG solutions.

Under the standard planning/design approach, 

a landscape architect would typically plan 

greenery to have an aesthetic effect and possibly, 

provide adequate shading for buildings’ thermal 

comfort and heat island reduction.  Selection 

for other functions such as evaporative cooling 

and phytoremediation (i.e. soil and water 

decontamination) would often not be considered. 

The BG Systems approach eliminates the 

possibility of these opportunities being missed.

Interactions between different urban components

Synergy Examples

The interactions between urban components are 

modelled in order to quantify and optimise the 

beneficial effects of their synergies, e.g.:

Reduce flood risks. To reduce flood 

risk, one may create a swale or other 

Sustainable Urban Drainage Systems 

(SUDS) element such as retention ponds or 

a multifunctional roof garden (Figure 12 a). 

These interventions involve interactions 

between Urban Solutions (topography), 

Water, Greenery and Climate Extremes. 

The model would quantify how much of 

the flood risk is being mitigated by this 

urban solution for a given return period 

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(e.g. 50 years). The type of greenery 

and the scale of the BG solution would 

influence its interactions and effects. The 

stored water will be used for irrigation of 

greenery, which will enhance biodiversity, 

urban agriculture and create natural noise 

barriers etc. 

Maximise the value of a tree. When 

planting trees in front of the south-facing 

Examples of BG synergies and their benefits

façade of a building, key interactions to 

map are those between Greenery (i.e. the 

tree and other vegetation on the site), 

Energy (building energy consumption) 

and Building Solutions (façade etc.). It is 

therefore vital to analyse the interactions 

and benefits of each species to determine 

how to achieve best performance against 

the set of prescribed functions (Figure 12) 

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Water

Greenery

Climate

Variability

Living

Environment

Quality

Urban

Solutions

Energy

Pollution

Building

Soulutions

$

Interaction of Individual BG Solutions

Benefits for healthier, more sustainable cities and developments

Using harvested storm water

to support greenery

Biodiversity

Living Environment Quality

Job Creation

Using recycled water for

energy efficiency and building solutions

Improved Urban Environment

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Blue Green Solutions Guide

Optimisation Process

The optimisation starts with the definition of a 

number of promising scenarios with different 

combinations of possible BG solutions. Simulations 

are then used to carry out a comparative analysis. 

A systematic optimisation is then carried out to 

rank the BG solutions and the optimal scenario 

is selected based on the criteria agreed with 

the client. Optimised solutions will be accepted 

if they offer lower life-cycle Costs, a higher level 

of efficiency, resilience and an enhanced Living 

Environment Quality. 

Cost-effectiveness of BG Solutions

A key advantage of the BG Systems approach is 

that it yields plans that are more cost-effective 

in terms of their Life-cycle Costs. Thus, the BG 

Systems approach offers a win-win situation: the 

developer will be interested because of increased 

client satisfaction (through intensive stakeholder 

involvement), higher Return on Investment 

(ROI), better sustainability, resilience and (green) 

credentials, whilst the city and local stakeholders 

benefit from a more sustainable, climate change 

resilient and greener cityscape.

The quantification of the life-cycle Costs is 

done using the Cost Dependence Matrix, which 

determines the possible cost reductions deriving 

from specific interactions between Urban 

Components. In quantifying these life-cycle 

costs, the full effectiveness of BG solutions can 

be demonstrated.

Consider a hypothetical example for surface 

flood reduction (Figure 13), which explores the 

interaction between an Urban Solution (change 

of street permeability and roof substrate 

thickness, for example) with Water (surface 

flood management). Apart from reducing surface 

runoff and thus flood risk, significant cost savings 

arise from the co-benefits: 

The option of using smaller, or even the 

avoidance in their entirety of, storm drainage 

and potable water pipes (savings in material 

and labour).

Water captured in tree pits and in surface and 

underground storage provide an additional 

water source for irrigation, leading to savings 

in the irrigation costs.

The storm water used to irrigate the greenery 

will lead to evaporative cooling and enhanced 

shading, thus reducing building cooling costs.

Climate Resilience Matrix

Climate change is associated with more frequent 

and more extreme weather events. Achieving 

urban climate change resilience therefore requires 

adaptation of urban planning practice in order to 

protect against these events

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. For this purpose, 

a Climate Resilience Matrix has been developed 

that identifies potential weather extremes 

affecting different urban categories, applicable in 

various parts of the world.

The BG Systems approach will investigate 

proposals for remedial measures designed 

to enhance the resilience of the BG Solutions 

themselves to weather extremes. This means 

that interventions such as tree pits and green 

roofs are better equipped to manage, for example, 

extreme rainfall events. 

The BG planning approach is guided by the A2R 

climate resilience approach (Anticipate, Absorb, 

Reshape)

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 and is designed to augment city/

project climate vulnerability assessment with a 

combined sustainability and resilience analysis. 

This process identifies appropriate resilience 

measures and integrates them with the BG 

sustainability measures already planned for that 

area. Integration of sustainability and resilience 

measures is instrumental to maximising the 

operating/resource efficiency and minimising the 

costs of the introduced urban BG solutions. 

The BG Systems approach ensures that the BG 

solutions will provide:

Decrease of risk, exposure and hazard.

Increase of coping capacity.

Compatibility with proposed project 

sustainability strategies.

Reduce air pollution. To reduce residual air 

pollution by traffic, in addition to tackling 

vehicle emissions, one could (for example) 

change access to and exits from the road 

area, as well as the movement of vehicles 

along the road itself. Determination of the 

best option involves mapping interactions 

between Urban Solutions, candidate BG 

Solutions and Pollution. One can use 

the matrix to look at the effect of using 

multiple BG Solutions and technological 

interventions: for example, combining 

pocket parks with trees, a rain garden and 

bio filters, with some of these measures 

also being used as traffic calmers in order 

to yield road safety benefits.  

Cost dependency matrix

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COMPONENT A

Urban Solutions

Street

permeability and

roof substrate

thickness

COMPONENT B

Water

Surface flood

management

BENEFIT 1

BENEFIT 2

BENEFIT 3

Surface runoff

smaller

Material and

labour savings

due to smaller

sewer pipes

Storm water

harvesting

Reduced potable

water costs due

to free irrigation

water and toilet

flushing

Storm water

harvesting

Energy savings

due to shading

and evaporative

cooling by

greenery

TOTAL CAPITAL COST

TOTAL RUNNING COST

Standard Cost

BG Cost

Ru

nn

in

g 

Co

st

Ca

pi

ta

l C

os

t

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