Mitcham Historical Society


Proud of our history and committed to our future

Mitcham Historical Society

Proud of our history and committed to our future

Mitcham Historical Society

Proud of our history and committed to our future

Letter
to Julia Gillard re Brownhill Creek Dam 04.04.12

               
Excerpt from literature: No Dam in Brownhill Creek
             
Website:  www.brownhillcreek.org
              
Facebook Page: No Dam in Brownhill Creek
                          
A concrete dam 12 metres high and 100 metres wide in the heart of Brownhill
Creek Recreation Park?

Damaging one of the world’s oldest parks:
Governor Grey set aside Brownhill Creek for public purposes in 1841, predating
the oldest National Parks in the world at Yellowstone USA (1872), Royal
National Park in NSW (1879) and Belair South Australia (1891).  Brownhill
Creek is now part of Yurrebilla, the Greater Mount Lofty Parkland.  The
Park Management Plan designates the area as a heritage site for
restoration, interpretation or safety works only.

The dam and road relocation will destroy the heart of the
park, which contains a traditional Kaurna camping site, a colonial heritage
rock-crushing site, an important plan rehabilitation site and state listed
threatened native fish species; Mountain Galaxias (rare) an Climbing Galaxias
(vulnerable).

Brownhill Creek is one of the last original creek lines in
the Adelaide Hills.  The Kaurna people called this area Wirraparinga
(place of scrub and creek) and the walking trail constructed in their honour
will be blocked.

The park provides a rural landscape less than 10km from the
city centre, a special place to retreat to for peace and exercise 
Activities in the park include picnicking, walking, running, cycling,
mountain-bike riding, horse riding and artistic pursuits such as painting and
photography.  Senior citizens, school, historical and tourist groups also
use the park.

There are viable alternatives to a dam in Brownhill Creek
that will improve flood mitigation.  More than ¾ of the catchment for
stormwater is below the dam site.  The dam will not give any protection
for the proposed 90 minute 1 in 100 year rain event over the urban catchment,
because flooding would have subsided before the peak flow arrives from the
catchment above the dam.  The dam will not provide protection for the
proposed 1 in 100 year 6-hour rain event over the Keswick creek
catchment.  The dam only provides protection for the long duration 1 in
100 year 36 hour rain event in the small catchment above the dam and there are
alternatives to take up the 6.5 cubic m/s flow required.

The vast majority of  flooding shown in official flood
maps is shallow, slow-moving water under 100mm in depth. 

The high hazard dam will be situated above a caravan park and
residential area.  No environmental impact study will be done before the
dam is approved.

The benefit to cost ratio for the overall project is .65
which means it costs 50% more than the economic benefits it provides.  The
benefit to cost ratio for the dam would be even worse because the destruction
of thousands of hours of works done in rehabilitating the park by school and
community groups and the cost to tourism, recreation and the environment, have
not been taken into account.

Other options are available:

Increased channel upgrades and high flow bypass culverts help
in all events. 
Channel clearing and maintenance in urban areas, incorporating new data from
the creek survey by the NRM authority, will reduce flooding.  
Small detention basins/wetlands.
Revegetation of cleared rural parts of the catchment can reduce run-offs by up
to 20%.
Improve building regulations to flood-proof new buildings by raising floors
above flood levels and by removing obstructions to flows.
Plan for the future and start a linear park.
Put in place an effective flood safe program.