An open letter to Melbourne Water and Kingston Councillors
Mr. Laurence Newcome
- cc Minister for Planning
- cc Kingston Council Officers
- cc Kingston Councillors
- cc Dingley Village residents
Floods in and around Kingswood Golf Course, also in much of the south of Dingley Village will exceed currently unacceptable levels if development proceeds
Dear Mr. Newcome,
Flood volume estimates for the proposed overfill of dwellings on Kingswood Golf Course, no matter how well calculated, are deeply inaccurate due to grossly underestimated input criteria.
The hugely lacking input statistics include no reference to floods in Golfwood close on the flood map, yet in recent years the floods were above knee deep at that location. It was at the height of water restrictions, so some residents washed their cars with the floodwaters.
Further, floods in Centre Dandenong road reach levels where they cannot possibly be allowed to reach higher levels (see photographs).
Most of all, at present the Golf Course park has 54ha of sandy loam soak, known for its ravenous water absorption properties. This soak acreage is greatly assisted by one of Victoria's largest aquifers below. Further - pumps run constantly in flood events, drawing water from the retarding basin onto the Golf Course holding dam.
The Aquifer was equipped and enhanced with State Government financial assistance not long ago - over $100,000 "down the drain", should the overfill proceed.
The interim building plans submitted to date will reduce this magnificient soak of nearly 54ha to an estimated 5ha, after blocks of units and blocks of buildings, plus roads and paths are in place.
Any household water collection will be overwhelmed by a sustained downpour.
Already the storm drains cannot cope with present rainfall downpours thus any further increase will causing further flooding on the roads. The base infrastructure cannot take away rains so what hope is there to take any extra.
Given all the above, the input criteria for Kingswood drainage calculations are hopelessly incorrect.
As we now make this flood information public, who can residents sue when we are proven correct?
At a meeting I attended with Melbourne water your organisation's staff stated that they were no longer permitting building where a development will export floods downstream, creating massive problems in other areas under Melbourne Water's responsibility, ultimately leading to increased bayside flooding.
Save Kingswood Group incorporated.
The addition of streets, driveways, buildings, patios, swimming pools, paths etc., creates impervious areas where surface water can no longer infiltrate. The greater the impervious area, the greater the runoff.
Drainage does not stop inundation if inadequate
Drainage in many developments receives less attention, and the result is greater than normal runoff occurring in the higher parts of the development, and the excess water flowing to the lower elevations in the development. The problems are almost always transferred downhill. (downstream)
The proponent's (developers) contractors have done modelling to avoid floods, but modelling and calculations only work if the input includes the information presented here by the Save Kingswood Group incorporated.
To date, the majority of proposed mitigation strategies and management plans have been heavily focused on controlling surface water sources; however they have missed flood events and mitigation strategies plus management solutions which only take into account overland flow may solve only part of the flooding issues.
The greatest risk of not understanding the groundwater dynamic during flooding events is the possibility of triggering unintended consequences of mitigation and management strategies.
Groundwater flood mapping is not a new concept. Flooding legislation recently introduced in Europe and transposed into law in the United Kingdom has recognised the importance of groundwater flooding by incorporating a requirement to assess the risk and undertake measures to reduce this risk where groundwater flooding is significant.
Melbourne Water no longer accepts excessive run-off from estates
From Save Kingswood: At a recent meeting with Melbourne Water we were advised that new estates can be well-drained, however when excessive inundation occurs, they then export their flood problems downstream. In this instance, apartments may have tanks to contain some water, however in regular downpours they overflow. This run-off plus the water from streets, will block input from existing residences in Dingley Village, increasing floods where there were less problems before.
They intend to leave almost no sandy loam soak uncovered, so the retarding basin capacity needs to be immense.
The photograph in section 1 shows the retarding-basin lake, which overflows. To reduce the flood impact, water is pumped into storage dams, but that buffer will reduce or cease to exist. So there’s the combined threat of hugely increased run-off, with massively reduced “soak” area.
There is also the immense Aquifer or underground water storage, which the Government reportedly contributed $100,000 to develop not so long ago. This is one of the best Aquifers in the country and should not be built on, due to loss of flood control and shifting soil foundation quality as it dries out. Construction within metres and lack of attention will also threaten the survival of native trees identified for retention.
“Land subsidence occurs where large amounts of ground water have been withdrawn from a thick layer of saturated fine-grained sediment that is susceptible to compaction. ... in some areas concentric cracks develop over smaller areas where compaction is occurring.”
Ref: Ground Water and the Rural Homeowner, by Roger M .Waller.
Below: Melbourne Water
At a meeting with Melbourne water attended by Save Kingswood, their staff explained they will no longer allow flood water from estates to cause huge problems downstream, even as far as Kananook Creek and further south.
Melbourne Water has demanded that any water excess to the norm resulting from floods in Kingswood must be contained within the development and only released at a rate that will not cause flooding in the rest of Dingley Village.
Therefore the proponent's contractors made calculations and plans for retarding dams, then announced that their overfill of houses will benefit Dingley Village, by stopping flooding elsewhere!
The floods modelling is based on inadequate data and ignores known flood events.
So no matter how many complex calculations are made, if the input data is wrong, so are the resultant findings.
As the developers build and bolt, yet this Save Kingswood Group Inc. document questions the hydrology data, who can residents sue when they are flooded?
From the proponent (developer)
Hydrology input underestimates the flood damage that will be caused to a great number of Dingley Village residences.
The proponent included the map below, however it is nearly 15 years old and does not take into account new buildings and increased water inundation upstream! It also does not show all floods that occurred.
Another plan, submitted by the proponent (applicant) ...
Even so, it states in a major downpour it "affects approximately 70 properties downstream of the site"
"Rainfall and Evaporation - Rainfall and evaporation data for Melbourne City with a range of 01/01/1966 to 31/12/1966 was used in the model"
Above: From the proponent's submission, item 6.2.2. MUSIC model setup. 1966!! Why is such old data used? Local inundation and houses upstream have increased or even dramatically increased since then.
Why "Rainfall and evaporation data for Melbourne City in 1966"?
Below: another map - flow path to wetland/retarding basin ...
Constructing a massive temporary retarding dam for stage one will create dust and chaos for the residents, resulting in extreme inconvenience, cause more asthma attacks and respirity medical conditions. Plus found to ruin electronic devices in their homes, from airconditioners to televisions to computer printers.
Snakes and wildlife will flee in terror into the backyards of about 150 homes that have easy access, most with open weave cyclone fence that was put up on their boundary by the golf club.
The current Dingley Village Special Building Overlay map below shows just part of the potential devastation coming if floods upstream in the Kingswood Golf Park are ignored
The Kingswood Golf Course Park already has a huge influence on existing flood zones in Dingley Village.
- SPECIAL BUILDING OVERLAY - purpose
- Shown on the planning scheme map as SBO with a number (if shown).
- To implement the State Planning Policy Framework and the Local Planning Policy Framework, including the Municipal Strategic Statement and local planning policies.
- To identify land in urban areas liable to inundation by overland flows from the urban drainage system as determined by, or in consultation with, the floodplain management authority.
- To ensure that development maintains the free passage and temporary storage of floodwaters, minimises flood damage, is compatible with the flood hazard and local drainage conditions and will not cause any significant rise in flood level or flow velocity.
- To protect water quality in accordance with the provisions of relevant State Environment Protection Policies, particularly in accordance with Clauses 33 and 35 of the State Environment Protection Policy (Waters of Victoria).
Flood areas on the map have been overlooked and/or greatly underestimated. (see below)
Each numbered area above is described below
Area 1 - the retarding basin and surrounding Golf Course sandy loam soil
Above and next three photographs: The retarding basin as it was when residents moved into Higgins close.
Below: The retarding basin currently cannot cope during floods
Note the "lakes" of water on the surrounding Golf Course and total overflow inundation of the Retarding Basin.
During large downpours water is pumped from the retarding basin and also floods onto the Golf Course. This causes short-term "acceptable" flooding, as the floods permeate into the sandy loam soil to the large Aquifer (natural underground water basin)
If the Golf Course is filled with Flats and Dwellings, a large four storey Age Care complex, footpaths and roads, this massive soak will cease to exist, resulting in previous inundation modelling being totally inadequate.
Below: the retarding basin overflow, flood level inundation in recent years.
Below: A garden table (from the house shown here) was swept away.
Area 2 at the bend in Greenwoods close
Floods have occurred here and a resident has contacted us, however there are no photographs.
Area 3 Golfwood close
Deep floods in Golfwood close - yet not shown in inundation plans!
Floods rushed from higher ground causing low houses in the top of Golfwood Close to be inundated. Number 45 is raised above ground level, but number 47 was inundated by water into the house. Carpets were destroyed inside, so new carpets had to be laid.
Over 10 cm of water surged against the garage doors at number 45, threatening damage, so the doors were raised. Water flowed through the garage, exiting on the back side fence into Willy court. The owner of the adjacent property in Willy court was extremely agitated when water inundated his property.
Floods in front of number 47 Golfwood Close were knee deep, so the water was used to wash their car.
A complaint was made to South East water. After they examined the area, an extra drainage pit was installed, yet the area flooded again after that installation.
The source of these floods appears to be from Greenwoods close to the north, which flows through a drain on the Golf Course. But the existing drain cannot handle the volume of water.
Again, this huge inundation is not shown on flood plans!
Area 4 next to Dingley Primary School
Below: Centre Dandenong road inundated, in the region south west of the Primary School.
Photographs show flooding at Torquay close Dingley Village, 20th February 2011.
This does show on a Special Building Overlay below, however the extent can only be seen in the photographs ...
After the flood at a residence in Torquay close. The water's peak can easily be seen
Area 6, Lee-Andy court
May 1, 2016
- I am in Lee-Andy court and have a storm water pit in my backyard and last night we flooded again. Like the times before the water pressure in the line burst the concrete pit lid right off and the water spewed into the backyard.
- I am wondering who else is along the same storm water line as me and if you flooded last night also?
- I know that last time this happened there were a few other people in the Golfwood close area backing onto the golf course that did.
- This happens whenever there is a large downpour and it is at the point where floods have lifted all of the pavers in the yard.
- Quite frankly I am tired of having to rush home from work or to get up in the middle of the night trying to sweep the water away so it doesn't penetrate the house.
But wait there's much more. Since writing this many more incidents in the central Dingley Village flood plain have been reported to us ...
Dingley Village shops, looking west (toward Golf Course) October 2011.