Creekcare

Whites Creek

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.

Diagram of a creek's meander 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

Urban Creeks and Wetlands
Vegetated Drainage Line (Photo Gillian Leahy)	Wetlands (Photo Aurora Sice)
Vegetated Rocky Creek (Photo Gillian Leahy)	Rocky Creek (Photo Gillian Leahy)

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.