Creeksbyted presents information about urban creeks. Whites Creek in Annandale, Sydney, Australia is of special interest to me and the Whites Creek Wetlands constructed by Leichhardt Council were initiated by me.

Web and blogs by Ted Floyd

http://ramin.com.au/creekcare

http://tedfloyd.wordpress.com

http://creeksbyted.com

Creekcare

All over Sydney and especially in the older suburbs many creeks have disappeared, buried in pipes or converted into ugly concrete drains. Swamps, water holes and flood plains are filled in and built over. Native wildlife is difficult to find and the fish are poisonous.

Creekcare and mimicking nature will encourage wildlife, purify water, reduce floods and maintain water flow in droughts. Restored creeks will become green corridors enabling native animals to migrate from suburb to suburb.

Sydney is now suffering from drought and we need to harvest water from clean creeks. Concrete canals should be attacked by jack hammers and made into eco-creeks surrounded by leafy valleys.

Ted Floyd
30 April 2007

REHABILITATION OF URBAN CREEKS

Ted Floyd
October 2010

Keywords: Urban Creeks, Waterways, Streams, Drainage lines, Stormwater drains, Grass waterways, Swales

Water flowing in creeks is a soothing gift from nature. Water gurgling over rocks, swirling in pools and spilling over waterfalls helps to wash our troubles away.

It is unfortunate many creeks in towns and cities have disappeared, buried in pipes or converted into ugly concrete drains. Swamps, water holes and flood planess are filled in and built over.

In growing cities trees are cut down, soils covered by impermeable surfaces and flash floods become common. Rainwater is collected in concrete gutters lining streets and flows down stormwater drains into rivers and the sea.

Stormwater drains are often dirty, lifeless, smelly and polluted. Ugly drains are a blight on the urban landscape. A natural creek is a great asset and attempts should be made to bring back nature to suburban stormwater drains.

Multiple use drainage systems.

In built up areas in towns and cities land is valuable and creek valleys should be used to satisfy a variety of needs. Valleys should be more than a single purpose drainage system.

• Parks and gardens
• Habitat
• Green corridors
• Sport and recreation
• Walking and cycle tracks with bridges
• Flood mitigation
• Pollution control
• Education
• Water storage
• Greenhouse control
• Shady, cool space
• Peace and quite

Habitat

Stormwater drains lined with concrete are sterile and support little life. Habitat diversity with aquatic plants and animals should be encouraged in the stream and natural habitat established in the riparian zone.

In creek valleys different ecological niches occur. The banks and flood planes provide special riparian habitat. Wetlands, billabongs, lakes and flowing stream provide aquatic habitat

Green corridors

Urban bush creeks facilitate the movement and migration of native animals in densely populated suburbs. Frogs, turtles and water dragons appreciate natural waterways.

Stormwater drains with concrete vertical walls act as a barrier to traveling animals. Creeks can be a watering place for thirsty animals and concrete walls prevent animals from enjoying a drink. Animal friendly streams are a great addition to the habitat of urban landscapes.

Floods and droughts

Stormwater drains are designed to remove floodwaters as quickly as possible from flood prone urbane areas. During droughts drains dry up or have very low flows.

The severity of floods and droughts can be reduced by treating the catchment by water sensitive design. Water should be stored in the catchment during rain periods to reduce flash floods.

Detention basins store water during rain periods and slowly release water after rain ceases. Water should be encouraged to infiltrate into soils and impermeable surfaces should be reduced. Water tanks store water for use in gardens during dry periods. Rain gardens, trees and wetlands can reduce flooding.

Catchment management and water sensitive urban design is a growing science with new techniques becoming available every year. The quality of stream rehabilitation is improved when the catchment is managed to reduce foods and increase dry weather flows.

Water flowing in a concrete gutter flows about three times faster than in a grass waterway. A meandering waterway has a longer length, reduced slope, slower velocity and increased water storage.

Flood planes and flood ways in drainage lines of rehabilitated creeks reduces the damaging effects of flash floods. Natural habitat can be established on flood planes where water only occasionally inundates the land.

In the ecological mix of a waterway, flood planes add a special habitat to a creek valley.

Pollution control

Toxic chemicals in a concrete drain are carried downstream untreated. In a flowing stream and in wetlands many chemicals are broken down into less toxic forms and harmful microorganisms destroyed.

Features of rehabilitated creeks

Many different natural features can be incorporated into rehabilitated creeks and the design will depend on the desired mix of end uses.

Rocky or earthen banks

• Meanders
• Pools and riffles
• Lakes and wetlands
• Islands
• Weirs
• Snags
• Flood planes and flood ways
• Bank stabilization with vegetation, natural rocks, sandstone blocks, riprap, logs, groynes

The physical layout of the land surrounding a creek will influence the design of rehabilitation works. Creeks in steep rocky areas similar to the sandstones in Sydney region are relatively straight, rapidly flowing creeks with waterfalls, rapids and small rock pools. The valley surrounding the creek is narrow with steep sides and small or no flood planes.

In western Sydney on the gently sloping planes, creeks meander and have earthen banks with extensive flood planes. Large pools and wetlands often occur in the drainage lines. Often flood planes have rich alluvial soils, prized by farmers.

It is important to remove rubbish and weeds. Pollution traps should be installed to prevent litter entering creeks. Silt traps prevent creeks from clogging up with sand and gravel. After construction regular maintenance will be required.

Environmental issues are global and often solutions are many local actions. We need to grow sustainable cities. Creeks and rivers are life forces flowing downhill through sterile built cities. Stormwater drains should be reborn in a manner similar to nature.

Creeks should be a pleasant cool space to visit and not a smelly dirty drain.

Links:

• Urban Catchments Enhanced By Green Corridors
• Catchment Care
• Whites Creek Catchment

The Story of Whites Creek Wetlands

Construction of Whites Creek Wetlands took the co-operation of Leichhardt Council, the NSW Government and Environmental Organisations.

While researching, on how to restore urban waterways in 1994, Friends of the Earth, Sydney identified a site for the construction of a wetland alongside Whites creek.

Completion of construction was celebrated with an Open Day on Sunday 20th October 2002. Council also initiated a successful community education program which won an Environmental Education award.

Wetlands improve water quality in the harbour by filtering out pollutants and nutrients.

Water from the creek is pumped into a settling pond where sand, silt and lead fall to the bottom.

A waterfall at the edge of the pond, agitates and aerates water adding life giving oxygen. Native plants absorb nitrogen and phosphorous in the next five ponds.

Nitrogen and phosphorus are essential nutrients for plant growth but encourage toxic blooms of blue-green algae in Sydney Harbour.

Eco-Annandale
Footprints EcoFestival
Sunday 6th June 2010
Photographs Irene Revel

www.ramin.com.au/creekcare

Mimicking Nature

 Creeks will be more pleasant and many benefits achieved when nature is mimicked in the surrounding catchments.

* Flooding is reduced. Volume of stormwater runoff is decreased and flood peaks are lower. The velocity of water in runoff and streams is slowed down, reducing the time of concentration and lowering flood peaks.

* Pollution is reduced. Vegetation and natural water courses filter water reducing pollution and sediment. Leaves are trapped in natural ecosystems.

* Habitat is improved. Native fauna and especially aquatic animals will be given a chance to flourish in unpolluted creeks. Natural habitats are more pleasant than concrete drains, adding to the aesthetic value of parks and gardens. Aquatic showpieces are valuable for school excursions.

* Popularity improved. Projects can be made more pleasant for the local population and this can create political pressure to spend more money on similar projects. Bigger concrete drains or gross pollution traps do not add aesthetic value for residents or visitors to admire and politicans seldom hear calls for more big, ugly, concrete pollution traps.

Raindrops are a heavenly gift from the gods landing on earth with a powerful thud. The energy in a little raindrop smashes uprotected soils into small particles formong a seal on the soil surface. Planting trees and ground cover mimicks nature and protects the soil surface from the beating action of raindrops.

When raindrops come to earth they are absorbed by the soil or if there are lots of them they will flow downhill over the land surface. The more rain absorbed by soils the more water available for plant growth. Large volumes of runoff can cause flooding in creeks and rivers further down the catchment.

Natural eco-systems absorb more water than suburburban soils. Large expanses of land in the suburbs are covered by buildings, roads and paving. These impermeable surfaces are sealed, preventing water entery. It is best to reduce the area of impermeable soils when possible so as to encourage soils to absorb water.

In natural eco-systems surrounding Sydney up to 70% of rainfall is absorbed by soils compared to 10% in the suburbs. In the suburbs a very high proportion of the rain immediately becomes runoff causing flash flooding.

Rainfall absorbed by soils is pumped back into the atmosphere by plants. Transpiration is the movement of water from soils up the roots and stems of plants and then out into the atmosphere through small holes in the surface of leaves. Water movement up the roots and stems is essential to carry plant nutrients from soils to the growing points of the plant.

In natural eco-systems transpiration by growing plants is a very important segment of the water cycle. About one half of rainfall in natural areas surrounding Sydney is pumped back to the atmosphere during transpiration by growing plants. In Sydney a large gum tree transpires up to 200 litres of water on a sunny summer day. Most drainage sytems are constructed using concrete and pipes ignoring the importance of trees. Planting trees and mimicking nature will increase transpiration and reduce flooding and drainage problems.

Water flowing through natural systems into creeks is cleaner. Natural eco-systems filter out pollution, sediments and leaves.

In stormwater drains the bends of natural creeks are straightened and rapid water flow is encouraged by smoothing the banks and stream bed. Many stormwater drains have concrete walls and often in densly developed suburbs creeks are buried in concrete pipes. Concrete drains are hostile to healthy plant and animal life.

To bring back life in suburban creeks the concrete needs to be ripped up and replaced with materials more sympathetic with nature. Concrete walls act as a barrier to travelling animals. Replacing concrete walls with gently sloping banks made from natural materials will build creek crossings for animals on the move. Mimicking nature by replacing concrete drains with eco-creeks, will help create green corridors.

Wetlands help to purify water and water flow in creeks is more even with less severe floods and increased flow in droughts. Habitat for aquatic plants and animals is provided by wetlands. Flood plains also help to reduce flood damage.

Small creeks should have waterholes, small waterfalls and short stretches of rapid flowing water gurgling over rocks. Creeks with rocky banks and beds are common in Hawkesbury sandstone country. Where Wianammatta shale occurs, creeks are often slower, meandering through gently slopping landscapes with clayey banks.

Whites Creek is a small creek in the densely developed inner western suburbs of Sydney.

The headwaters are in the suburbs of Stanmore and Leichhardt and the creek flows in a northerly direction between Annandale and Lilyfield into Rozelle Bay, Sydney Harbour (Port Jackson).

The creek’s length is a little over 2 kilometres and the catchment area is 262 hectares. The highest point in the landscape is 44m above sea level in the Southern headwaters.

About 55% of the land is covered by houses and units with a population of 14,000. Total road space is 25% and only 3.5% of land is parkland. The largest park is Whites Creek Valley Park with an area of 6 ha.

All native bushland has disappeared and the complete length of Whites Creek is now a stormwater drain with buried pipes in the upper reaches and an open concrete cannal for the lower 1 kilometre.

Water pollution in the creek originates from all land areas in the catchment. The major source of water pollution is leaks from sewage pipes and runoff from roads.

www.ramin.com.au/creekcare/whitescreek-catchment.shtml

Whites Creek Wetland

The constructed wetlands beside Whites Creek are designed to remove nitrogen and phosphorus from polluted stormwater.

Biodiversity is increased by the creation of a dynamic aquatic ecosystem and the aesthetic features of a popular park are improved. The wetlands are now an excellent field centre for the demonstration of water sensitive urban design.

Water is continually pumped from the creek into a settling pond where sand, silt and lead fall to the bottom. Water then flows over a small waterfall into the first pond. The waterfall agitates and aerates water adding life giving oxygen.

Native plants growing in the ponds absorb nitrogen and phosphorous from water. Nitrogen and phosphorus are essential nutrients for plant growth but encourage toxic blooms of blue-green algae in Sydney Harbour.

Water flows through 5 ponds and is aerated by small weirs between ponds. The depth of each pond is differnt, from one third to one half a metre allowing a variety of plant species to survive.

Frogs and native fish are now breeding successfully. Striped Marsh Frog, Common Eastern Froglet and Perons Tree Frog all add to a loud cacophony of croaking frogs on warm spring nights.

• Lilyfield 3 km from Sydney CBD, Australia
• Whites Creek flows into Rozelle Bay, Sydney Harbour
• Parking, Wisdom Street; Buses on Booth Street, Walking path Whites Creek
• Initial concept by Friends of the Earth, 1996, built by council Aug 2002
• Owned by Leichhardt Council, Funding $244,500 Stormwater Trust grant
• Area 1,000 sq m, depth 0.3-0.5m, estimated volume, 300kl
• Catchment area for wetlands, 161ha, Whites Creek catchment 262 ha
• Flow rate, 6 litres/sec, 200 Ml/year. Floodwater bypasses wetland
• Rainfall (Observatory Hill) 1,200mm/yr

.

http://www.ramin.com.au/creekcare/whitescreek.shtml

these articles are an extract from Ramin on the web

Water Cycle in Urban Catchments
Water is essential for all life on earth. About three billion years ago life began as small microscopic
marine organisms. Nearly 300 million years ago primitive amphibians crawled out of their watery
home on to dry land. Humans appeared about 1 million years ago. Since then our numbers have grown
enormously and our way of life has had profound consequences for the water cycle, particularly in
urban areas.
The water cycle begins with water being evaporated by the sun mainly from the sea, which becomes
vapour and forms into clouds. Some of the cloudy vapour blows inland where it falls as rain before
eventually flowing back to the sea.
The main source of fresh water is rainfall runoff which is widely used to meet human needs. Runoff is
a vital part of long-term water supply and renews all water resources, be they rivers, lakes or reservoirs.
Most plants living on land have roots buried in the soil and these plants absorb life-giving water from
the soil. Nitrogen, phoshporus, calcium and many other essential plant nutrients are found in soils and
are carried up into the stems and leaves by water.
There is a continuous cycle of water on earth and the total amount remains close to a constant. The
driving force is the sun evaporating water from the sea, lakes and plants. Water cycle in soils is
especially important for the growth of plants. When rain falls onto the earth, water is absorbed by soils
and excess water flows over the land into creeks and rivers. Water may evaporate from soils or filter
down through the soil to the water table. Plants absorb water from soils and the water is evaporated
from leaves into the atmosphere, completing the soil water cycle.
Every creek, river and lake is surrounded by a catchment and seperating each catchment is a divide
where water flows on the other side in the opposite direction into the neighboring catchment. The total
catchment should be considered in water management schemes. When possible it is best if management
schemes begin in the upper catchment.

Artificial water cycle
In cities the man made water cycle is an addition to the natural water cycle. The Artificial water cycle
includes: town water supply, watering of parks and gardens, sewage system including the leakage of
sewage into creeks and stormwater drains. Many suburban drains always have a water flow, even
during long droughts because of artificial sources like excessive watering of gardens, washing cars and
washing footpaths.
Precipitation
Precipitation is water falling from the atmosphere to the earth as rain, hail, snow, sleet, fog or
dew.
When rain falls on the earth, it is first intercepted by vegetation which covers the land. A small
proportion of the rain is evaporated directly from plant surfaces. Water is collected in the upper canopy
of many tree species, flowing down the stems and trunk into the soil helping to improve water supply
to trees surrounded by concrete and tar.
During rain, water is stored on the surfaces of leaves and stems. When it ceases to rain water will
continue to drip from trees. Leaf drip helps to even out the intensity of storms and may have a small
effect on reducing flood peaks.
Evaporation
An evaporimeter is used to measure the rate of evaporation directly fom a water surface. In Sydney the
annual evaporation of 1800 mm is higher than rainfall, 1200 mm. The ratio between
evaporation/precipitation is the P/E ratio and is a measure of the water available from rain for plant
growth. In Sydney the annual P/E is 0.67, in summer months P/E is less than 1 and as low as 0.33 and
in winter months evaporation drops to 80 mm/month and the P/E rises to 1.7. This data indicates the
high evaporation in summer months restricts plant growth and homegardens, especially lawns need to
be watered to keep plants growing.
The above data demonstrates evaporation is highly significant in Sydney. The climate in many cities in
the world is different and evaporation is lower especially in the Northern cities of London and New
York.
Water is also directly evaporated from surface soils into the atmosphere. Evaporation is faster from
bare soils than protected soils. Mulches protect soils directly from sunlight and reduce water loss by
evaporation. Mulches also insulate soils, keeping them cooler during summer months and reducing
evaporation. Water evaporation from garden soils is a waste of water and in times of drought should be
prevented.
Transpiration
Growing plants transpire water into the atmosphere when they absorb large volumes of water
from soils, which travels up the roots and stems to the leaves. Water evaporates through
stomates, which are small pores in the leaf surface, into the atmosphere.
Water travelling up the stems transports minerals from soils up to the leaves where organic substances
are manufactured for plant growth. Trees transpire large volumes of water. In Sydney a large gum tree
transpires up to 200 litres of water on a sunny summer day.
Direct sunlight is the driving force of transpiration. Trees with a large leaf area transpire water quickly
and high up in the canopy, winds blow moisture away encouraging faster transpiration. Native trees are
evergreens and transpire water in all seasons, while very little transpiration occurs in deciduous trees
during winter when they lose their leaves.
Deep roots enhance transpiration. Many Australian native trees have very deep roots, up to 40 metres in
favourable soils and often the roots of large trees reach down to the water table. During dry spells,
surface soils dry out and native trees with deep roots continue to grow using water in the subsoil. This
helps to make native trees drought resistant. In suburban Sydney the roots of trees sometimes penetrate
into sewage pipes and are able to survive in the driest droughts.
Quick growing native trees have the ability to transpire 2-4 times more water in a year than the average
annual rainfall.
During the severe drought of the early 2000’s in Australia, the depth to the water table increased.

Unfortunately many native trees died in country landscapes because of a lack of water and the inability
of roots to reach down to deep water tables.
Grasses have shallow roots. Annual grasses have very shallow roots often less than 0.5 metres deep.
Permanent grasses have deeper roots and kikuyu roots can be as deep as 2.5 metres. Lawns with
shallow rooted grasses need to be regularly watered at frequent intervals during hot summer weather.
Many lawn grass species are not native to Australia and are not suited to hot dry summers and need to
be watered regularly to be healthy and green. In drought prone Sydney water can be saved by
replacing thirsty lawns with drought proof native species.
Paths and roads made of concrete or tar restrict water entery into soils, but transpiration can occur from
soils covered by impermeable surfaces if plant roots have spread under the path or road. If a tree
canopy spreads over an impermeable surface, the rate of transpiration will depend on the area of the
canopy and not on the smaller area of permeable surface.
Evapotranspiration is the sum of evaporation from surface soils plus transpiration from plants.
Scientists often study evapotranspiration because it is easier to measure than to separately measure
transpiration and evaporation.

Stormwater
Water which does not infiltrate into soils becomes surface runoff which flows downhill eventually
concentrating in rills, creeks and rivers. A small amount of water is trapped in puddles and
becomes depression storage.
Undisturbed creeks meander through trees, bushes and grasses with flood plains waterholes, riffles and
waterfalls. Swamps purify and store water. Aquatic plants and animals thrive in natural ecosystems.
In urban areas, many original creeks are buried in pipes or bulldozed into straight concrete canals.
Living native ecosystems disappear under the sterile drainage systems of the councils engineers. Fish
have difficulty surviving in the polluted water.
Flash flooding is a problem in suburbs with concrete drains and where soils are covered with
impermeable surfaces. Roads, buildings and other impermeable surfaces prevent water entering soils
and all the water flows into stormwater drains. Natural drainage systems store water in swamps and
flood plains reducing the severity of floods. Creeks have bends and meander through a valley slowing
down the water velocity.
A short time of concentration is another factor increasing flood peaks. The travel time from the most
remote point of the catchment to the outlet is the time of concentration. In urban catchments water
flows faster, the time of concentration is shorter and flood peaks higher, compared to rural or natural
catchments
Water flowing in a concrete gutter flows about three times faster than in a grass waterway. Ecodesigned
waterways which meander increase length of the waterway and reduce the slope. Waterways
incorporating natural features will reduce the velocity of water flow and reduce flood peaks.
Straight, concrete canals are designed to swiftly drain water downhill away from upstream, flooded
areas and can increase flooding downstream. Eco-designed drainage systems remove water slowly
from flooded areas but reduce floods downstream. The design of drainage systems need to have a
balance between these factors.
Landform surrounding creek systems varies greatly, especially when the geology varies. In Sydney
creeks running through areas of Hawkesbury Sandstone geology group, are found in narrow, rocky,
steepsided valleys. The creeks flow swiftly along the steep gradient with riffle zones and small
waterfalls. These creeks have small flood plains, few bends and do not meander.
In Western Sydney many creeks meander through flat flood plains. On the Wianamatta Shale geology
group, a common landform is gently undulating hills and creeks meandering through floodplains.
Along the Nepean River valley there are extensive ancient floodplains dissected by creeks.
Many new housing developments increase flash flooding when swamps and floodplains are filled in
and built on. Culverts and bridges built in the earlier rural landscapes are now often too narrow and act
as a dam during heavy rain, blocking the flow of creeks and causing flooding upstream. Stormwater is
increased in new housing developments because of the extensive areas of impermeable buildings and
road surfaces.
Water sensitive urban design is now used in new suburban developments. Houses, buildings, gardens
and drainage systems are designed to reduce water wastage and stormwater flow. Flooding can be
reduced by reducing concrete paving, installing rainwater tanks and encouraging water infiltration into
soils. Water detention basins temporarily hold and gradually release water after flood peaks. The
severity of droughts can be reduced by harvesting stormwater and using the saved water in the home block.
Water Table and Groundwater
Groundwater is found in saturated subsurface soils or rocks. The upper surface of groundwater
is the water table.
Rainwater entering soils is returned to the atmosphere by evaporation and transpiration and excess
water percolates down to the water table. The water table rises during rainy seasons or falls in dry
periods.
When the water table comes to the surface a spring will form. The water table comes to the surface at
rivers or lakes. The supply of ground water helps to keep rivers flowing when it is not raining. After
heavy rain when the water table rises, intermittent springs may form.
Leakage occurs when water percolates down below the root zone and down to the water table.
The water table depth is equal to the depth down to the water surface in a well. A piezometer can be
used to measure water table depth by drilling a small hole in the soil down to below the water table.
The hole will fill up with water to the water table depth. Using two or more piezometers and measuring
the difference in the water table between different piezometers enables the direction of groundwater
flow to be determined.
Water Catchments
Drainage basin for a stream or lake is the water catchment. A catchment is the area determined
by topography where surface runoff from rain will flow downhill in drainage lines and then into
a stream. The divide or watershed is a ridge separating neighbouring catchments.
Rainwater falling in a catchment follows a number of different processes. Evaporation returns water
back to the atmosphere. Runoff water flows overland down to creeks, streams and rivers and eventually
flows to the sea. Water infiltrating into the soil provides water for plant growth and is returned to the
atmosphere by transpiration. Excess water in soils percolates down to the watertable and eventually
seeps into creeks and rivers.
Water balance in a undisturbed catchment in Sydney region
Interception by plant surfaces 15%
Runoff 15%
Seepage to groundwater and rivers 10%
Evapotranspiration 60%
Total 100%
In natural catchments 70% of annual rainfall is absorbed by soils. The amount of water absorbed by
soils in one rainy day varies. Water absorption is lower if the soil moisture content is high and water
runoff is greater during heavy storms. Water absorption will vary in different parts of a catchment
depending on topography, soil type, vegetation cover and other natural characteristics.
Swamps and bogs store water when it rains and gradually release water into creeks during dry weather.
Water is purified in swamps. Swamps are a very important feature in natural catchments and are often
filled in and built over in urban catchments.
Many creeks and rivers have flood plains. Water flows onto flat land surfaces on the sides of rivers
during heavy storms. Flood plains act as a large water storage resevoir, reducing down stream flooding.
Levee banks built on one side of a river can increase flooding on the opposite side of the river.
Natural catchments are altered in many different ways by people. The first victims are often trees.
Cutting down trees reduces water infiltration into soils increasing surface runoff and flooding. The
water table rises after trees are cut down and transpiration is reduced.
Erosion may be a problem after trees are cut down and farmed with poor management practices used
when growing crops and grazing animals.
Roads alter the water characteristics in a catchment. Roads can act as barriers to natural drainage lines
concentrating water into artificial drains. Water can back up causing flooding behind bridges and
culverts with a small capacity. Water runoff from poorly designed roads can cause erosion.
In towns and cities catchments are greatly altered and many problems may occur including flooding
and pollution.

Water balance in high density urban catchment
Runoff up to 90%
Evapotranspiration and seepage to ground water 10%
Total 100%
Rain falling onto the impermeable sufaces of roads, paths and buildings becomes surface runoff and
flows into the council drainage systems.
Home gardens, streetside nature strips and council parks have permeable surfaces. Water absorbed by
garden soils is used by growing plants and is transpired back into the atmosphere. Excess water in soils
percolates down to the water table.
Natural drainage lines, creeks, swamps, wetlands, billabongs and anabranches are filled in and
destroyed when suburban drainage systems are rebuilt. The natural features of catchments help to even
out waterflow, reducing floods and maintaining flow in dry times.
Councils often used swamps and flood plains as garbage dumps. The garbage was covered with a layer
of soil and a park created. These parks were flat and made ideal football fields and cricket grounds.
Councils called this “land reclamation”. The destruction of swamps and flood plains causes
environmental havoc, especially increased flooding and pollution from the garbage dumps.
When streets and houses are constructed land is levelled, drainage lines filled in and runoff collected in
surface gutters running alongside streets. Gutters on the surface collect little seepage from soils. Urban
drainage is efficient in removing surface runoff and not very effective in draining waterlogged soils.
Floods
Flash floods occur in urban areas. Flood peaks are higher in urban areas because there are more
impermeable surfaces and water flows faster down concrete drains. Urban drainage systems reduce
flooding upstream from the drains and sometimes flooding may be increased in the downstream water
disposal area.
In natural catchments flood peaks are lower and water flow in dry weather is more reliable. Natural
wetlands and swamps help to even out water flow in creeks and rivers. Water flow is slower in
meandering creeks, and rocks and fallen trees act as obstacles. During rain, swamps absorb water and
slowly release water into creeks during dry weather. Water infiltrates into permeable soils and some of
this water seeps down to the groundwater and slowly percolates into creeks and rivers. Flood plains are
filled in and built over increasing flood heights.
Total Catchment Management (TCM)
In total catchment management, all the issues of land, water, and natural resources are managed
throughout a catchment and not limited in area by man-made boundaries.
In TCM, the natural boundaries of ridge lines, creeks and rivers are used to divide the landscape into
management units. All the relevant issues are considered together to form a comprehensive plan of
natural resources, including the interaction of different resources.
A high level of co-operation is required to achieve a successful total catchment management program.
Often a catchment covers land in more than one local government area and different issues are the
responsibility of a number of relevant State Government Departments including, Sydney Water,
Department of the Environment and Department of Natural Resources. Many companies and
individuals own land in catchments.
Catchment boundaries are seldom the same as local government council boundaries and in Sydney
most catchments cover more than one council. Councils are responsible for the part of the catchment
within their boundaries and are not interested in what happens on the other side of their boundary.
Water does not know where council boundaries are and problems created on one side of a boundary
will easily flow downstream into a neighboring council. Total catchment management is needed to
solve problems involving two or more councils.
One hundred years ago diseases spread through swamps and creeks polluted with effluent from
unsewered suburbs. Typhoid, dysentery, measles and even an outbreak of bubonic plague occurred in
the inner suburbs. The Bondi sewage outlet was completed in the late 1800’s and swamps were drained
and polluted creeks filled in and converted to concrete drains. Houses were connected to the sewage
system and fresh water was obtained from the Nepean River. Sydney Water (Water Board) was
responsible for major water issues and councils responsible for local drainage.
Catchment management was mainly concerned with the construction of concrete pipes and drains
designed to remove flood waters very quickly away from the problem area. These concrete drainage
systems reduced flooding where they were constructed and unfortunately they sometimes added to
downstream floods.
In the last 30 years people have become aware of water pollution as a major environmental issue.
Pollution is the responsibility of the Department of the Environment (Environment Protection
Authority). Pollution, flooding and drainage are now all considered as important urban stormwater
issues. The water in Sydney Harbour is now cleaner and it is a good sign to see whales entering the
Harbour. Problems still exist and Sydney Water needs to stop sewage leaking into stormwater drains.
The new issue in Sydney is drought and the drying up of the water storage dams in the mountains.
Nearly all of the rain falling in the suburbs becomes stormwater causing floods and flowing quickly
down concrete drains. Rain is precious and should be harvested for usefull purposes. Sydney Water is
responsible for providing freshwater to homes and industry.
The New South Wales Government recognises the importance of Total Catchment Management. In
1984 the Government introduced a State TCM Policy. The formation of a network of Catchment
Management Committees was initiated in the Catchment Management Act 1989. TCM is the
responsibility of the Department of Natural Resources.
The Sydney Metropolitan Catchment Authority (SMCMA) is preparing a catchment action plan (June
2006). Catchment plans now need to include schemes to droughtproof Sydney. Water harvesting
schemes are needed to capture rain for useful purposes.
Water Sensitive Urban Design, WSUD
WSUD is complementary rather than antagonistic to the natural water cycle. Suburban areas
should be more compatible with natural hydrological and ecological processes with on-site
collection, treatment and utilisation of water flows.
Many on-site technologies are now used to reduce flooding and pollution. Often pollution loads are
higher in floodwaters and the control of flooding can reduce pollution.
Flooding can be reduced with on-site technology in the upper catchment, reducing the necessity for
concrete pipes and drains designed to carry water downhill with the possibility of causing more severe
flooding. Multiple use technologies are now commonly used. Garden water tanks are a proven way to
save water for the home garden and reduce stormwater flood peaks.
In heavy storms leakage of sewage into stormwater drains commonly occurs. Stormwater harvesting
for irrigating parks is now recommended by the State Government and unfortunately stormwater is
often highly polluted with sewage.

Carbon Cycle in Soils

1. Photosynthesis in green leaves CO₂ in air synthesised into sugars
2. Sugars transported in stems to all parts of plant
3. Exudates from roots deposited in soil and becomes food for microorganisms
4. Plants eaten by animals and respiration produces energy and CO₂ returned to atmosphere
5. Leaf litter forms from dead leaves, bark and stems
6. Soil organic matter
7. Microrganisms
8. CO₂ is released during respiration by insects and microorganisms and
9. Inorganic plant nutrients are released into the soil in a soluble form available to plants.

WATER and CARBON in GARDEN SOILS

Vigorous plant growth, irrigated by water harvesting will establish carbon sinks in urban gardens.

Water cycle

Water harvesting: Water collected from the roof of a house and used to irrigate the home garden. Water can be stored in a water tank and used in dry times or water from the roof spread directly on the garden during rain periods.

When raindrops come to earth they are absorbed by the soil or if there is too many of them they will flow down hill over the soil surface.

Transpiration is the movement of water from soils up the roots and stems of plants and into atmosphere. Water movement up roots and stems is essential to carry plant nutrients from soils to the growing parts of the plant.

Excess rainfall is not absorbed by soils and flows downhill over the land surface into drains and creeks. Flooding is reduced when more water is absorbed by soils and less water allowed to enter drains.

Water harvesting reduces downstream flooding and reduces severity of droughts in gardens. Organic matter improves water penetration into soils and increases water storage in soils.

Irrigation increases plant growth. The use of town water may not be available in the future and to ensure good plant growth in urban gardens water harvesting is necessary. Water tanks are very useful and storage of water in soils will help plants to grow in dry times.

Water collected on the roof of a house and spread over a garden area of equal size to the house, doubles the total rainfall. For this to work the soil has to be well prepared. The ground surface needs to be very permeable to allow water to soak down into the earth.

IMPROVING WATER INFILTRATION INTO GARDEN SOILS

• Increase plant cover to protect soil surface
• Encourage plants with deep roots
• Improve soil structure
• Add mulches, green manures and compost
• Encourage earth worms
• Add soil improvers such as gypsum
• Maintain rough soil surface
• Protect the soil from raindrop impact
• Reduce soil compaction
• Improve subsurface drainage
• Use organic fertilizers and animal manures

Growing plants encourages water to penetrate deep into soils. A variety of plants with different root systems will allow water stored in the soil at different depths to be utilized.

Carbon sinks

Carbon dioxide in the atmosphere causes greenhouse effect and air temperatres to rise. A carbon sink is created when carbon is removed from the atmosphere and locked up in a form away from the atmosphere and not causing a rise in air temperature.

Photosynthesis: In green chlorophyll of plant leaves, organic compounds are synthesised using energy from sunlight, water from soils and atmospheric carbon dioxide CO₂.

Photosynthesis is the basic process producing food and energy by plants. Animals eat plants and each other and there food and energy is originally synthesised by photosynthesis.

Respiration:Plants and animals use oxygen from atmosphere and living compounds to produce energy and exhale carbon dioxide CO₂ to atmosphere. All living organisms respire including plants, animals and microorganisms.

In a mature native forest the rate of photosynthesis is nearly equal to the rate of respiration. There is a balance and no CO₂ is added or subtracted from the atmosphere. If the forest is cut down photosynthesis in trees stops and respiration by soil microorganisms continues and extra CO₂ is added to the atmosphere increasing the greenhouse effect. If trees are planted and nurtured in cleared land and photosynthesis is faster than respiration a carbon sink will form.

Carbon sinks can be formed from any plants growing at a faster rate than total respiration. In most farming land respiration is faster than photosynthesis so CO₂ is added to the atmosphere.

Carbon sinks in urban gardens are created by living plants growing above and below the ground surface. Green plants absorb carbon dioxide from the air and manufacture plant material by photosynthesis in leaves.

Below ground level, organic matter in soils is a very important carbon sink. Leaves and stems fall onto the soil surface, forming a leaf litter. Many small animals and microorganisms break down large dead plant remains into small pieces, incorporating broken down plants into soil organic matter.

Benefits of soil organic matter

• Food for microorganisms and soil animals
• Nutrient cycling
• Store plant nutrients in soils
• Reduce harmful changes in soil acidity and alkalinity
• Improve soil structure
• Improve soil aeration
• Reduce erosion
• Increase water infiltration
• Improve water holding capacity
• Create healthy soils and encourage vigorous plant growth
• Are a very good carbon sink and reduce greenhouse gases

Organic matter in soils is found in varying stages of decay. On the soil surface plant residues occurs including leaf litter and mulches. Particulate organic carbon is small plant remains, humus is very small particles synthesized by microorganisms. Charcoal is mainly carbon and is resistant to decay, lasting for hundreds of years.

Plants are made from sugars, starches, cellulose, fats, oils, proteins and lignin. Sugars are very quickly eaten by microorganisms, cellulose is slowly converted to sugars and lignin is very resistant to decay and may survive in soils for hundreds of years. Organic matter is mainly dead, decomposing plant material. Only a small proportion originates from animals. Animal bones, CaCO₃ is a inorganic compound containing carbon.

The amount of carbon is often equal above and below ground level. Carbon in soils increases in cold or wet conditions. Woody plants, containing lignin, forms humus resistant to microbial breakdown and will persist in soils for hundreds of years.

Carbon sinks will be bigger when there is extra plant growth in soils with desirable physical properties.

The build up of soil organic matter by returning garden cuttings, compost and mulches to soils will add nutrients to the soil. The addition of organic materials to soils will improve soil physical properties. Structure is stable, improving soil aeration and water movement. Water holding capacity is increased, improving drought tolerance. Damage from erosion and the beating action of raindrops is decreased.

Cultivation and digging soils can reduce soil organic matter. Digging soils increases aeration and this can increase the decay of organic matter. Cultivation kills plants and this can reduce the build up of organic matter.

Hardwood trees and shrubs and especially gum trees form long lasting humus in soils.

Well managed garden soils will contain up to 10% organic matter. A small gum tree can store up to 1 tonne of carbon with ½ half above ground and ½ half in the soil. It is possible to store 4 tonnes of carbon in 100 square meters of garden containing several trees.

During a hot summers day trees will cool a backyard garden and strategically positioned plants will cool a house. Tall trees provide welcoming shade and growing plants transpire water from their leaves into the air producing a cooling effect.