PAT CONDINA & ASSOCIATES Consultants in waterway, wetland and lake management, Water quality monitoring and assessment, Community consultation and education
Overview of Flood Drainage Capacity of the Dalmore Road Drain with reference to Drains in the Koo Wee Rup Longwarry Flood Protection District
Report prepared for Landowners in the Dalmore locality August 2012
Aspromonte Enviro Pty Ltd (ABN 31 074 579 936), Trading as Pat Condina & Associates Director - Pat Condina, M. Env. Sc., Grad. Dip. Water Sc., Dip. App. Chem. 17 Olive Rd., Devon Meadows, Victoria 3977 Telephone & Fax. 03 5998 2034 Email: [email protected]
Drainage Capacity of Dalmore Road Drain and KLFPD Drains
TABLE OF CONTENTS
Executive Summary ...... 3 1. Introduction and Scope of Study ...... 6 2. The Catchment and KLFPD Background ...... 7 2.1 The Westernport Catchment ...... 7 2.2 The Koo Wee Rup District and the Great Swamp ...... 8 2.3 Drainage in the Koo Wee Rup District ...... 10 2.3.1 Brief History of Drainage ...... 10 2.3.2 Significant Flow Events in the District...... 12 2.3.3 Flood Risk and Flood Protection ...... 16 2.3.4 Carrier Drains, Precept Drains and District Drainage Charges ...... 17 2.3.5 Maintenance of Carrier Drains and Precept Drains ...... 19 2.3.6 Drainage impact of Upstream Development ...... 20 3 The Dalmore Road Drain Catchment ...... 22 3.1 Drainage area and land uses ...... 22 4. Capacity and Condition of Dalmore Road Drain ...... 24 4.1 Factors Effecting Theoretical Flow Capacity ...... 24 4.2 Dalmore Road Drain Surveys ...... 25 4.3 The Floodgates on Dalmore Road Drain ...... 28 4.4 Possible Sources of Drain Sediment ...... 29 5. Observation Following June 2012 Storm Event ...... 31 5.1 Dalmore Road Drain Condition and Levels ...... 32 5.2 The Diversion to Cardinia Catch Drain ...... 34 6 Potential Strategies to Improve Drainage ...... 38 6.1 Drainage Improvements by Landowners...... 38 6.2 Drainage Improvements by Councils...... 38 6.3 Drainage Improvements by Melbourne Water ...... 38 6.3.1 Improve Drainage Capacity of Dalmore Road Drain and other Precept Drains ...... 38 6.3.2 Prepare 5 year plans for Carrier Drain and Precept Drain Maintenance ...... 39 6.4 Clarification of Regulatory Restrictions ...... 39 6.5 Summary of Problems and Potential Responses ...... 41 REFERENCES ...... 43 APPENDICES ...... 44 Appendix 1 Monthly Rainfalls ...... 44 Appendix 2 Melbourne Water Community Newsletter ...... 47
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
Executive Summary
Scope of Study
This Report was commissioned by Landowners in the Dalmore Road Drain catchment who were adversely affected in the February 2011 and June 2012 floods, and by earlier flood events. The Landowners have contended for many years that, if proper maintenance and infrastructure is in place, the Dalmore Road Drain would service its catchment. This Report supports the Landowner’s contention with reference to data and the author’s physical observations.
While partly technical, the Report aims to increase Landowner understanding of the drainage system in their locality, measures to improve that system, the risk of flooding, and how such risk could be managed.
It also aims to: • Document observations of flow and condition in the Dalmore Road Drain during the June 2012 flood; • Identify potential mitigation measures for Melbourne Water’s consideration and assessment, to improve the drainage characteristics of the Dalmore Road Drain and other drains, and • Provide an overview of drainage in the Kooweerup Longwarry Flood Protection District (“KLFPD”) with reference to level of protection, flood drainage capacity and other challenges in both “Carrier” drains and “special Precept” drains.
The Westernport Catchment and District Background
The KLFPD covers an area of approximately 420 km2, and is totally within the wider 2980 km2 catchment draining to Westernport Bay. It is one of the most important food production areas in the state.
The 40,000 hectare Kooweerup Swamp was drained in the late 1800’s to early 1900’s, by construction of over 500 km of major and minor channels to convey stream flows from the upstream catchment, and local runoff through the Swamp, to Westernport Bay.
The draining and clearing of the Kooweerup Swamp was the largest swamp reclamation scheme undertaken in Victoria and resulted in major hydrological changes, accompanied by equally significant changes in the generation, transport and export of stormwater pollutants to Western Port Bay.
The extraordinary flood of 30 November/1 December 1934 resulted in flows never seen before or since with great loss of property and stock. The subsequent Royal Commission noted the deficiencies in the drainage system and recommended that substantial improvements be made. The completion of the spillway at Cora Lynn in 1962 to divert floodwater into the Yallock outfall and so protect the township of Koo Wee Rup was the last major work to take place in the KLFPD until the Main Drain rehabilitation works in 2001.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
The key issue for the continuing sustainability of the KLFPD is the level of flood protection provided, and the level of drain maintenance to achieve required protection. While residents and farmers may be accepting of losses from major flood events every 30, 50 or 100 years they will not be accepting of losses every 10 or 15 years. Loss of crops is not just related to size of the flood, it is probably even more dependent on duration of high levels in drains for long periods after rainfall ceases, as this prevents effective drainage of surrounding land. In recent years District landowners have expressed concern over perceived lack of adequate maintenance on Carrier and Precept drains and the consequent increased risk of overtopping, longer periods of land inundation, and crop losses.
Landowners in the KLFPD pay a special “Precept” rate rather than the normal Metropolitan waterways and drainage rate. The Precept rate is to cover flood mitigation and maintenance services carried out by Melbourne Water on the extensive network of drains and channels within the District. In 2009/10, $980,907 was collected from 3544 properties within the District boundaries.
The District is subject to external influences which may impact on the overall flood risk. This includes sea level rise and increased stormwater flows from the expansion of the urban growth areas to the north in the Shire of Pakenham and the City of Casey.
The Dalmore Road Drain in the June 2012 flood event
The Dalmore Drain catchment comprises a drainage area of 1075 hectares from Cardinia Road north of Cardinia to the outlet at Westernport Bay. By reference to site observations and past surveys this Report concludes that drain flow capacity has been diminished by sedimentation and the growth of bed and bank vegetation.
The recent 21/22 June 2012 storm event highlighted the inability of the Dalmore Road Drain to effectively drain its contributing catchment within a reasonable period of time to ensure that pastures and crops were not adversely affected by flooding. In this event, the period of inundation would have been somewhat higher than normal even in a clean drain situation as the soil was initially wet.
During inspections a number of Landowners voiced their concern that levels in the Dalmore Road Drain had not dropped within a reasonable time. There were similar concerns expressed about the levels in Tooradin Inlet Drain. Four days after the storm event it was clear that Drain levels were still near the top of banks, and flow velocity was very low. It was evident that flow rate and velocity was being limited by vegetation growth in the Drain and sedimentation of the bed.
On the morning of 26/6/12, in response to the emergency situation on many properties faced with potential losses of high value asparagus crops, a diversion was placed in the Dalmore Road Drain. Following this diversion Drain levels dropped quickly and surface water on adjacent properties was able to flow into the Drain. It was concluded that sedimentation and growth of mangroves between the South Gippsland Highway and the tidal floodgate (situated some 1330 m upstream of the South Gippsland Highway), and emergent plants upstream of the floodgate, had reduced Drain flow capacity. The physical restriction of flows through the floodgate was also a potential factor, along with high tides further restricting flow downstream of the floodgate.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
Regulatory restrictions on vegetation removal from drains, imposed on Melbourne Water as the Drainage and Waterway manager, can also constrain that authority’s capacity to undertake timely and adequate maintenance on the Dalmore Road Drain and other district drains.
Potential strategies to improve drainage
Improvement strategies can be implemented at all scales from property drainage to major catchment drainage. Accordingly this Report considers potential works and strategies that can be adopted by Landowners, Councils and Melbourne Water to improve drainage and reduce flood associated impacts in the District. Generally this includes improved maintenance regimes particularly on drains where deficiencies have been noted. In some cases this may need to be preceded by appropriate technical investigations.
A critical issue for resolution is the regulatory constraint on some drains in the District concerning removal of vegetation and other works, and on the well-being of certain protected species. In particular the application of certain provisions of the Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act) has resulted in cessation or postponement of some maintenance or other essential works. While all native vegetation and fauna has value, it is undeniable that the system of drains in the District was constructed many years ago for the specific purpose of providing drainage and flood protection so that farming activities could be undertaken. As such the maintenance and service capacity of the drainage system should be exempt from such regulatory restriction. Melbourne Water needs to be active in ensuring that the constructed drains are excluded from policy changes in the first instance, rather than in obtaining special approvals for works after the changes.
As for any farming activity, the aim is not just to survive but to prosper. The District is the heart of the Bunyip Food Bowl. Even basic survival will be threatened if the Districts drains and outlets to the Bay are blocked with sediment and vegetation.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
1. Introduction and Scope of Study
The flood event of 21st and 22nd June 2012 and the earlier event in February 2011 again highlighted the importance of adequate drainage capacity for flood prevention. Such flood events are often widespread and flooding is reported in many parts of Melbourne. However flooding in the KLFPD has an added dimension of concern as the whole District is completely dependent for its continued existence and productivity on the adequate maintenance and replacement of a complex system of drains, floodways, floodgates and other flood protection infrastructure.
In the recent June 2012 flood, the Dalmore Road Drain overtopped at several locations upstream and downstream of the railway, and stayed at high levels for a number of days, so large areas of surrounding crop lands were inundated. While the areal extent of inundation is of concern, Landowners and especially those growing high value crops are even more concerned with the period of inundation of land. Inundation periods of more than 2 or 3 days will result in losses or serious impairment of pasture grasses and high value crops such as potatoes and asparagus. The issue is not one of inconvenience; it is one of livelihood, and the ongoing viability of the District.
This Report was commissioned by affected Landowners in the Dalmore Road Drain catchment. While partly technical the Report’s aim is to increase Landowner understanding of flood risks in their District and describes measures to improve performance and reduce risk. Accordingly the Report aims to: a) Document observations of flow and condition in the Dalmore Road Drain during the June, 2012 flood and assess the role of drain maintenance on drain capacity and flooding of adjacent lands. b) Identify potential mitigation measures for Melbourne Water’s consideration and assessment, to improve the drainage characteristics of the Dalmore Road Drain and reduce both areal extent of inundation and periods of land inundation following flood events. District wide mitigation measures are also discussed. c) Provide a brief overview of drainage in the Kooweerup Longwarry Flood Protection District with reference to levels of flood protection, flood drainage capacity, and other challenges in both Carrier drains and special Precept drains (see 2.3.4).
A more complete understanding of the problems in the Dalmore Road Drain can be better achieved within the context of the development of the Westernport Catchments and the draining of the Great Swamp to form one of the most economically productive agricultural areas in Australia. Accordingly this Report will also briefly examine the overall catchment context.
In many respects the Dalmore Road Drain is representative of flood drainage capacity issues in the KLFPD. It may well be that these issues developed over the years between 1997 to 2010, but were not readily apparent during that period as the lower than normal rainfalls and reduced soil wetness resulted in reduced impact in storm events. The recent situation is different with higher rainfalls over the last two years leading to more saturated soils so that even smaller storm events may result in more noticeable and widespread flooding.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
2. The Catchment and KLFPD Background
The KLFPD covers an area of 420 km2 and is totally within the wider 2980 km2 catchment draining to Westernport Bay. It is one of the most important food production areas in the state. As an example, the district produces over 90% of Australia’s asparagus, estimated at over $50 million annually, and is a large seasonal employer. High yield potato growing, dairying and beef production are also major District industries.
The following sections will consider the impacts of historical development of the catchment and in particular the draining and development of the Kooweerup Swamp, once the largest swamp in Victoria.
Throughout this Report the spelling ‘Kooweerup’ is used when referring to the Swamp, as it is an official historical place name more in keeping with the Aboriginal name. When referring to the town or district, Koo Wee Rup is used.
2.1 The Westernport Catchment
The Western Port catchment today is in a vastly different condition to its state when first settled by Europeans in the early 1800’s. The dense forest covering the country below the ranges and the extensive wetland complexes that dominated low-lying areas (formerly known as the Great Swamp) have almost disappeared. Clearing of the forest commenced in the 1800’s to establish sheep and cattle runs. Most of the wetlands were drained to gain access to the rich peat soils. In particular, the “inefficient” natural drainage patterns that were critical to the water balance of the wetland systems have been replaced by highly efficient and highly connected drainage systems that rapidly convey stormwater runoff borne pollutants through the stream networks to the Bay.
Today, the population of the Western Port catchment is widely distributed across the catchment, living primarily in 25 towns and villages. The population grew from 45,000 to 150,000 between the early 1970’s and 1999, and has continued to grow even more rapidly since as urban growth corridors have been expanding from the Port Phillip Bay catchment to the Western Port catchment.
Recent estimates of current land uses provided by the Department of Sustainability and Environment (based on assessments undertaken by the Department of Primary Industry) indicate the following land uses in the Western Port catchment:
• Forest - 46,088 Ha (15.5 %) • Rural (grazing and Horticulture) – 238,449 Ha (80.0 %) • Urban including industrial – 13,392 Ha (4.5 %)
The main sub-catchments in the Westernport catchments are those of the Bass, Lang, Lang, Bunyip and Tarago Rivers and Cardinia, Deep and Toomuc Creeks on its northern shore, and the sub-catchments of Watsons Creek, Merricks Creek, Stoney Creek and Main Creek on its western shore.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
The Swamp was not one vast body of shallow water overgrown with reeds and rushes. It consisted of many discrete shallow and deep marsh areas often separated by very low sandy rises, with a complex maze of disconnected channels throughout. The rivers entering the Swamp are shown on Table 1 along with their catchment areas upstream of the Swamp, and their annual discharge in megalitres (ML).
Table 1 Rivers draining to the Great Swamp (adapted from Roberts 1985) River Catchment Area km2 Average Annual Discharge ML Bunyip/Tarago at Iona 686 106,000 Tarago 233 56,580 King Parrot 62 5670 Heifer and Musk 62 ~ 5000 Lang Lang 370 73,700 Ararat 101 ~ 10,000 Deep 83 ~ 7000 Toomuc 72 6680 Cardinia 173 11,100
Under natural conditions, flood flows were highly attenuated by the Swamp and smaller event flows may have been damped out altogether. The hydrological consequences are summarized in Table 2 derived from Brizga et al (2002).
Table 2 Effect of Draining of Kooweerup Swamp on Flood Characteristics Parameter Before Draining (1890) After Draining (from 1920) Flood Velocity 0.18 m/s 1.85 m/s Flood Storage 75 million cubic metres 17.4 million cubic metres Time of flow to Bay 3-5 days 2.3 hours
Modelling in the Brizga (2002) study also showed there were large increases in the total volumes of annual surface runoff generated by the catchment as a result of loss of forest cover and increase in impervious surfaces arising from development.
The draining of the Swamp also accelerated waterway erosion processes in the streams draining to the Swamp. By the time remedial erosion control measures were undertaken, particularly from 1989 to 1995, severe headward erosion had advanced many kilometres upstream in the Bunyip and Lang Lang Rivers and Cardinia, Deep, Toomuc and Ararat Creeks.
The major hydrological changes described above were accompanied by equally significant changes in the generation, transport and export of stormwater pollutants to Western Port Bay. The following processes were evident:
• In its original state the Kooweerup Swamp was an extremely effective pollution retention and filtering mechanism, so limiting the amount of suspended solids, nutrients, organic matter, and other pollutants entering the Bay.
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• Fast-flowing waters from the upper catchment would enter the Swamp, spread out and lose their velocity. This resulted in deposition of coarse and fine sands at the Swamp margins near the inlet points. • In all but the largest flow events this water would be retained in the Swamp for up to several months allowing further deposition of finer silts and clays and uptake of nutrients by algae and aquatic plants.
A Review of Urban Stormwater Contaminant Impacts on the Streams and Marine Environment of Western Port and Catchment (Pat Condina & Associates, 2005) made estimates of such increases through modelling of land uses and associated hydrological changes. That review found that loads of suspended solids, total phosphorus and total nitrogen had increased by 274%, 256% and 216% respectively compared to pre-settlement loads.
2.3 Drainage in the Koo Wee Rup District
2.3.1 Brief History of Drainage
The most thorough record of the history of the KLFPD is the publication “From Swampland to Farmland” by David Roberts (1985). Following the settlement of Port Albert in the 1840’s the Great Swamp was increasingly seen both as a barrier to movement by horse and ox drawn carts, and as a potential land area for cattle fattening and for growing crops. Land around and on the Swamp was taken up from 1839 onwards.
The draining and clearing of the Great Swamp was the largest reclamation scheme undertaken in Victoria and was initially documented by East, (1935). While isolated drainage channels were dug as early as 1857 (by William Lyall), larger drainage schemes only commenced in 1885 under direction of a “Swamp Board”, and afterwards continued by the Department of Public Works in connection with a scheme of village settlements for absorbing unemployed people from Melbourne.
The Main Drain (Bunyip River) drainage system was essentially excavated by 1905, but succeeding floods in 1911 and 1923 showed major deficiencies in the system so additional improvement works continued. In 1917 the lower portion of the Swamp was constituted as the “Lower Koo Wee Rup Flood Protection District” and the western portion separately as the “Cardinia Flood Protection District”.
The extraordinary flood of 30 November/1 December 1934 (292.6 mm at Gembrook and 170.2 mm at Koo Wee Rup) resulted in flows never seen before or since and resulted in great loss of property and stock. The subsequent Royal Commission noted the deficiencies in the system and recommended that the two districts should be combined under one authority, and that substantial drainage improvements should be made. Options of upper catchment retarding basins and additional channel capacity were examined after the Royal Commission (for example by Ritchie, 1937). The two districts were eventually amalgamated in 1962 as the Koo-Wee-Rup Flood Protection District, and subsequently as the Koo Wee Rup Longwarry Flood Protection District (KLFPD) in 1995, thus including low lying areas of Drouin West and Longwarry which drained into the Swamp from the northeast.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
The completion of the spillway at Cora Lynn in 1962, to divert floodwater from the Bunyip Main Drain into the Yallock outfall and so protect the township of Koo Wee Rup, was the last major work to take place until the Bunyip Main Drain rehabilitation works in 2001. The first major test of the Yallock Outfall was in November 1971, when peak flows of 238 m3/s (similar to the flows in the 1923 flood which caused widespread flooding and damage), were recorded at Iona. According to Roberts, (1985), apart from necessary road closure at the Yallock system at the South Gippsland Highway, there was no significant property flooding. If this was in fact the case then this flow sets a benchmark for Main Drain capacity in a fully clean state.
Management of the drains in the district passed from the Rural Water Commission to the Dandenong Valley and Westernport Authority (DVWPA) in November 1989, and subsequently came under the control of Melbourne Water with the merger of the Melbourne and Metropolitan Board of Works with the DVWPA and other Authorities in 1991. There has always been landowner representation on some form of Flood Mitigation Advisory Committee. The present committee is called the Koo Wee Rup Longwarry Flood Mitigation Advisory Committee. The Committee meets at 3 monthly intervals at Melbourne Water Office in Koo Wee Rup. Its role is to provide a representative ratepayer-based forum for advice to Melbourne Water on maintenance and works priorities within the KLFPD so that the special Precept rates collected in the district (the total of which is based on the level of service required as identified by the Committee) may be spent efficiently and equitably.
Figure 2 Koo Wee Rup in the 1934 Flood
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
2.3.2 Significant Flow Events in the District
The KLFPD has flooded many times in the last century. The following table summarises these significant events (derived from Melbourne Water Bunyip Main Drain Investigation Report, 1998, some flows slightly different to earlier SR&WSC estimates given in Roberts, 1985)
Table 3 Historical Peak Flows in Bunyip Main Drain at Iona Year Peak Flow Peak Flow Total Rainfall mm Estimated 3 (m /s) source (ML/day) ARI MW, 1998 from Roberts 1985 (years) April 1901 93 17,122 i.e. 198 217.4 Jindivick m3/s 1911 127 1918 192 Oct 1923 219 21,600 i.e. 250 m3/s Aug 1924 347 27,900 i.e. 95.7 Jindivick 323 m3/s 1932 141 Nov/Dec 1934 859 97,840 i.e. 316.1 Jindivick and 170.2 >200 1132 m3/s KWR 1935 277 Oct 1937 524 48,920 i.e. 100 566 m3/s 1944 132 1951 177 1952 284 1953 219 Sept 1959 184 120.3 Jindivick, 79.4 KWR 1960 120 Nov 1971 238 19,445 i.e. 225 148.5 Jindivick, 53.1 KWR 17 m3/s 1984 184 15,900 i.e. 184 10 m3/s no overtopping Oct 1990 147 14,400 i.e. 108 Gembrook 8 166 m3/s overtopping 1996 132 2004 116 Feb 2011 152 (183 est.) 18?? June 2012 76 80.2 KWR
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
It should be noted that the runoff in any storm event will be related to prior weather conditions. In general if the catchment soils are wet or saturated there will be a higher proportion of surface runoff and less infiltration.
East (1935) first documented this effect in the Bunyip catchment. He noted that flood discharges in storms occurring in summer months gave lower peak flows than those occurring in winter and spring months. Actual figures quoted by East are shown below converted into metric units. In the case of the August 1924 flood, East estimated that approximately 60% of the rainfall on the catchment was discharged as stream flow within 4 days after the cessation of the storm.
Table 4 Comparison of Seasonal flows (adapted from East 1934) Date of storm Rainfall mm (mean Flow m3/s Bunyip Main event Beenak and Longwarry) Drain at Iona Summer December 1930 104 88 Months March 1931 153 82 Winter and October 1923 77 251 Spring August 1924 113 323 Months October 1932 88 130
Dale (1974) further noted the large annual flow variation that can occur and compared the highest annual discharge in 1934/35 of 303,860 ML with 100,000 ML in 1973/74 (gauge area not reported). The latter year yielded a water generation factor of 0.66 ML/km2 /day.
It is interesting that for many years the former State Rivers and Water Supply Commission calculated that the capacity of the Bunyip Main Drain just above Cora Lynn was about 230 m3/s. This was however based on a “Manning n” roughness co-efficient of 0.03 (see Section 4.1), whereas even in a well cleaned out drain 0.045 should be used, and where there is extensive in- stream vegetation even a figure of 0.08 could be used (Melbourne Water, 1995). Accordingly in more recent times MW has estimated that the actual capacity in the Main Drain was 150 m3/s due to cross sectional area restrictions and vegetation growth. Apart from vegetation in the channel, it is understood that capacity restrictions were imposed by the bridge at the 11 Mile Road and bank setback restrictions imposed by the road encroachment and alignment at the top of the bank.
The 2001 works aimed to increase capacity to 210 m3/s. Melbourne Water (2001) noted that as an indication of the flood risk from drain overtopping, there have been 12 flood events above 150 m3/s between 1900 and 2000 and only 8 events above 210 m3/s. It is understood that not all of the works planned in 2001 were completed due to external regulatory constraints placed on Melbourne Water, so the proposed capacity of 210 m3/s was not fully achieved up to 13 Mile road.
In the February 2011 flood, the Bunyip Main Drain overtopped again upstream of Cora Lynn, near Iona, and widespread losses occurred. It is understood that there was no overtopping between 11 and 13 Mile Roads and that overtopping occurred in the heavily vegetated section upstream. Here, the drain banks were heavily damaged by uprooted trees and bank slumping (see photos 1 and 2). The flow gauge reading at overflow was 152 m3/s at Iona, and the modelled peak flow was 184 m3/s, (Cardno, 2012), showing that the actual capacity in 2011 was well
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains below the 2001 estimates of proposed capacity. The modelling results of the flood investigation of the 2011 storm also indicated that removal of vegetation would have lowered flood levels at Iona sufficiently to ensure that flows did not exceed the capacity of the Main Drain at this location.
The Cardno 2012 report also observed that “the modelling also indicated that if the vegetation was reduced, water levels in the Bunyip River downstream increased to a point where the levees surrounding the River-Yallock Creek Outfall confluence would be breached causing additional flooding of the Koo Wee Rup township in the February event”. This observation is questionable as the historical function and flow relief capacity of the Yallock Outfall is understood to actually prevent downstream flooding of Koo Wee Rup in this type of event. The only way such an observation could be accurate is if the capacity of the Yallock Outfall downstream of Cora Lynn was now heavily restricted by vegetation and sediment, which is unlikely. It would however be appropriate for Melbourne Water to clarify the current flood capacity of the Yallock Outfall and Bunyip Main Drains.
Similar reasoning regarding vegetation effects would apply to other drains in the district including Dalmore Road Drain, i.e. the risk of flooding over the top of banks will be reduced significantly if woody plants are removed and are not allowed to grow on drain inner banks. Such removal (and hence risk of overtopping) is to a certain extent cyclical as each drain could not be subject to maintenance every year and some drains may not receive attention for 3 or 4 years, even on a planned maintenance program.
In recent years external constraints based on protection of native habitat and native species have been placed on Melbourne Waters ability to maintain drains and remove vegetation from some drains in their control, either directly or as a consequence of de-silting (see Section 6). Such constraint has even extended to vegetation removal within the Main Drain. Unfortunately there has been too little recognition that these are drains constructed several generations ago for a very specific purpose. A whole community and an important agricultural area depend entirely upon the continuing effective function of these drains.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
Photo 1 Bunyip River upstream of Iona showing extensive bank vegetation regrowth
Photo 2 Bunyip River showing bank damage after Feb 2011 Flood event
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
2.3.3 Flood Risk and Flood Protection
Flood risk is always present in the KLFPD. Level of risk is commonly evaluated by consideration of both the likelihood of an event (i.e. the chance of occurrence of a particular event) and the consequence of the event (for example whether catastrophic, major, moderate or minor). The level of risk often determines the type and amount of protection measures that will be required. Where a significant risk is identified, protection measures must be introduced to reduce the risk to an acceptable level.
Evaluation of flood risk is complex and dependent on both physical and social considerations. Expressed most simply, a high rainfall event will produce a high runoff from the catchment on which it falls, which if not contained in a channel(s) could result in land flooding and loss of crops, stock, property and even life. The key components of this chain of events are tabulated Table 5 below: Table 5 Description of components of a flood event Component Discussion of component of a flood event Rainfall The key characteristics defining a rainfall event is rainfall intensity (in mm/hr) and duration in event hrs) at rain gauges in the catchment. From this the Average Recurrence Interval (ARI) of the storm can be calculated. For example a 100 year ARI event would occur on average once every 100 years. However such is the nature of chance that it could well or 2 or 3 times in that period. Alternatively, looked at from an annual basis the chance of such an event occurring or being exceeded in any one year is called the Average Exceedance Probability (AEP). Thus a 1% AEP vent has a 1% chance of occurring in any year and is equivalent to the 1 in 100 year ARI event Runoff The level of runoff response in any catchment in terms of peak flows is particularly dependent from the on the type of cover on catchment surfaces and the infiltration capacity of the soil. A larger proportion of impervious surfaces (i.e. hard surfaces such as roofs, sealed roads, and concrete catchment paths) will result in less infiltration into the soil and more surface runoff. Soil wetness at the time of the storm is also critical. For example even a rural catchment would respond similarly to a fully urbanized catchment if the soils profile was saturated at the time the storm arrived. The chance of a particular peak discharge (i.e. rate of water flow in terms of volume over time) occurring in a storm event is similarly expressed as the rainfall above. For example a 20 year ARI discharge event would occur on average once in 20 years and its AEP would thus be 5%. Conveyance In any event surface runoff is conveyed to major channels draining the catchment (eg the of Dalmore Road Drain in the case of the Dalmore Road Drain catchment) via overland flow and minor drainage lines. This will occur more quickly if drains are efficient as in the case of pipes floodwaters or well connected clean open drains The chance of a channel being overtopped in a storm event in channels depends on its flow capacity. For example if a channel can accommodate 20 year ARI event without overtopping then it is said to have a 20 year ARI capacity and AEP (i.e. chance of overtopping) would be 5% in any year. This of course assumes a certain channel size and condition – two factors which can change with time and frequency of maintenance. Duration of While this is dependent on the pattern and duration of rainfall and efficiency and connectedness flood of drains, it is also dependent on the flow capacity of the drains and especially of the main outfall channel of the catchment. Runoff may reach a main channel, however if flow velocities inundation in the channel are very low due to say blockage in its lower section by sediment or vegetation, then drain levels will remain high for longer periods and hence water covering surrounding land cannot be easily drained.
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It can be seen from the above table that a certain ARI rainfall event can result in different ARI runoff depending on the condition of the catchment at the time of rainfall, and the ARI capacity of any drain also varies over time, depending on its condition.
The key issue for the KLFPD is the level of flood protection provided. While residents and farmers may be accepting of losses from major flood events every 30, 50 or 100 years they will not be accepting of losses every 10 or 15 years. For example it may be that farmers will accept flooding of their land once every 10 years and limited crop losses once in 20 years, but not more frequently. Similarly they may accept that once every 100 years there may be a devastating flood that results in total losses and destruction of local infrastructure and in such flood the prevention of loss of life and protection of homes must be the greatest priority.
Loss of crops is not just related to size of the flood, it is probably more dependent on duration of high levels in drains. For example a twenty year ARI flood which results in land inundation may not result in any crop losses at all if the drains are in a clean condition and levels recede within a day or two of cessation of rainfall.
Future documentation by Melbourne Water of the design capacity, ARI, and current capacity of each drain under their management and control, would assist Landowners to understand and assess the risks to property and crops. In addition Melbourne Water in consultation with Landowners should establish a clearer understanding of the cost, levels of protection and associated maintenance programs that are currently provided. Such information may well lead to decisions for additional drainage capacity to be provided and/or infrastructure upgraded. Such decision would be based on cost/benefit considerations and can only be made on complete knowledge of the options.
2.3.4 Carrier Drains, Precept Drains and District Drainage Charges
It would be fair to say that historically the emphasis within the KLFPD has been on the capacity of the Bunyip Main Drain and other large “Carrier” drains, i.e. the drains that convey upstream catchments runoff water through the District. This is understandable because of the risk to human life and property in the event of catastrophic failure of this system in a major flood event. Apart from the Bunyip Main Drain, other Carrier drains include the Western Contour Drain, the Cardinia Creek, Gum Scrub Creek, Toomuc Creek, Deep Creek, Ararat Creek, the Number 7 Yallock (King Parrot Creek) and the Number 6 Yallock (Musk, Heifer and Sandy Creeks).
This past emphasis on the Carrier drains and the desire to attain a more sustainable waterway for river health purposes has resulted in the extensive Main Drain Rehabilitation works previously described. But it is clearly apparent that attention needs to be focused on the remaining 400 km of District drains (i.e. the local “Precept” drains, so referred because a special Precept rate is levied on ratepayers in the District for their maintenance) and the numerous associated levees, floodgates and other structures managed by MW. The Precept drains were constructed as civil infrastructure assets to service the District whenever there was significant local rainfall. The potential economic losses from flooding and extended inundation from these Precept drains could be even more significant. At a lesser scale still there are also the roadside drains managed by Casey and Cardinia Councils.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
As at 2009/10 there were a total of 3544 properties within the KLFPD. Landowners pay an exclusive charge to cover maintenance services for the extensive network of drains and channels that service the District and mitigate flood risks. This is known as a Precept rate. It varies between Precept area A, set at 3.649 cents in the $ of property Net Annual Value (NAV) in 2010/2011, and Precept area B, set at 2,027 cents in the $ of property NAV. The differential rate is seen as due to differences in requirements for drainage services. There is minimum rate of $54.60. In 2009/10 a total of $980,907 was collected with estimates for 2010/11 being $1,001,684 (source Melbourne Water KWRLFM Advisory Committee Pricing Paper, 2012.)
As the Bunyip Main Drain and other Carrier drains carry flows from upstream of the District it is valid that their maintenance be predominantly funded from Melbourne Water’s general drainage rate revenue rather than the precept charge.
From 1 July 2012, Melbourne Water will change the way it calculates its Waterways and Drainage Charge throughout the Metropolitan area (but not in the KLFPD). A South East Water brochure advising of this change states that “this will share the costs of delivering important flood protection, public health and environmental benefits for waterways more fairly across property owners in Melbourne”. The new charge will be a flat rate of $85.08 on each dwelling on a property title. If this was applied to the KLFPD then about $300,000 would be collected. It could thus be argued that this amount should be spent on the Carrier drains which benefit the general community, with the remainder of the Precept rate (i.e. over $700,000) going to maintenance of Precept drains. Alternatively, and more equitably, the cost of Carrier Drain maintenance (not capital works which should fall entirely to Melbourne Water) should be shared between Melbourne Water and KLFPD ratepayers so it would be more appropriate for the ratepayers to contribute $150,000/annum with the remainder of $850,000 going to precept drain maintenance.
It is essential that this amount of money be spent annually to maintain the Precept drains, and furthermore there is a case that can be made that extra funding should be contributed by Melbourne Water and the Councils to compensate for additional works required as a result of the impacts of upstream development as described later in this Report. The former Dandenong Valley Authority recognised the reality of such impacts and imposed an additional drainage scheme charge on new developments which specifically set aside funds for work in downstream areas to mitigate the impacts of upstream development.
There is a proposal to change the KLFPD rating system, proposed to apply from 1 July 2013 (Melbourne Water, Draft 2013 Water Plan). It is proposed to no longer use property values to set rates and to apply only one Precept rate for each property title in the District. This is a very important proposal with significant implications for equity and levels of service in the District.
The extent of the District, its major drains, and rate divisions are shown in Appendix 2 to this Report, which reproduces a recent Melbourne Water Community Newsletter discussing proposed changes to the rating system.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
2.3.5 Maintenance of Carrier Drains and Precept Drains
Drain capacity and drain maintenance are the most important factors in flood protection. Unfortunately there is little written record of the historical level of service in terms of actual drain capacity and maintenance. In the past, it was understood that every drain would be subject to a defined maintenance regime and that woody plants would not be allowed to grow on banks. For example, anecdotal evidence would suggest that a drain would be sprayed at least every second year to eliminate plant growth on bed and banks which would otherwise impede flow and trap sediment. Then every five years the drain would be de-silted along its full length by use of a long reach excavator.
By way of example the KLFPD annual Report 1986/87 (Rural Water Commission of Victoria) described some of the maintenance activities at the time as shown in table 6 below:
Table 6 Drain Maintenance Activity in Mid 1980’s Maintenance Activity Actual 1985/85 Actual 1986/87 Projected 1987/88 km of Drains km of Drains km of Drains Chemical Weed Control 161 198 183 Mechanical Cleaning 40 119 63 Total Drain Maintenance 201 316 246
It can be seen that at the time up to half of the length of the District’s Drains received attention each year. It is essential that current maintenance programs continue the standards established in earlier years. It is difficult to compare past drainage works programs with current programs. Melbourne Water operating budgets for the District for 2009/10 showed that revenue was $980,907 and total expenditure was $883,700 of which $573,100 was spent on Precept drains and $310,600 was spent on Carrier drains. Vegetation control was the highest component with $242,400 spent on the Precept drains and $141,600 spent on the Carrier drains. By comparison a relatively low amount was spent on de-silting with $75,400 being spent on Precept drains and $24,800 on Carrier drains.
The recent Melbourne Water Community Newsletter shown in Appendix 3 notes that “for many years the Precept rate paid for the full cost of the maintenance of the Carrier drains. Discussions between the Advisory Committee and Melbourne Water have identified that since the Carrier drains also serve a purpose beyond the Precept area, the maintenance costs should be split equally between the Precept rate and Melbourne Water. This new cost sharing arrangement has been backdated over the life of the current method of setting the Precept rate to 1 July 1999. As a result, Melbourne Water will allocate $4.5 million (in today’s dollars) to the Precept to undertake drainage-related projects for the benefit of the community”. This is a very positive acknowledgement, however the implication is that lower than optimal amounts may have been spent on Precept drain maintenance in recent years.
One isolated example of changes in historical maintenance that could affect flood levels is sand removal from channels. In the early 1930’s it was calculated that net accumulation of sand in the Main Drain was 54,000 cubic yards over a five year period, amounting to a deposition rate of 1
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains inch/annum (SRWSC 1936 works report). Sand continued to be removed on a regular basis from the Main Drain and Cardinia Creek and other creeks until recent years. General observations would indicate that there is far less sand removed today than was historically the case. This could be due to stabilization of stream channels and hence reduced generation of sand. Notwithstanding this it would be informative if MW assessed current sand depths within say Cardinia Creek and the lower section of the Bunyip Main Drain below the railway line, to ascertain whether there has been any reduction in flood conveyance capacity.
2.3.6 Drainage impact of Upstream Development
It is clear from the above discussion that there have been many floods in the District and floods will continue to occur. Landowners are clearly aware of this risk of flooding and to some extent are accepting of such events. This acceptance however is within the context of knowing that all feasible prevention and risk mitigation measures have been taken.
The flood issue comes to the fore at frequent intervals in the District. The headline on Page 54 of the Pakenham Gazette of 5 July 1995 was “Farmers worried floods will happen more often”. The article noted the need to control runoff from increasing upstream urban development. Since that time urban development in the Casey Cardinia Growth Corridor has increased markedly.
From a surface water runoff perspective, post-settlement changes have resulted in a highly modified hydrological response by the catchment. Initially this was through conversion of forest woodland and Swamp to rural uses. In more recent times there has been increasing urban and industrial development in the catchment.
Urban development to the north of the district KLFPD stretching from Berwick to Pakenham now covers an estimated area of about 4000 hectares. The hydrological response of such development includes
• More frequent drain flow events • Higher peak flows as water flows quickly off hard surfaces • Higher runoff volumes as less water infiltrates into the ground.
While Melbourne Water drainage schemes associated with these developments will include flow detention and retardation measures and water quality treatment, there is still considerable downstream change - in particular:
• The retardation basins on each development reduce the peak flows (the aim being to restrict flows to pre-development flow rate levels) however the result of this is to prolong medium flow periods within the drains.
• With a reduced time of concentration in the urban catchments, stormwater reaches channels far more quickly so the downstream channels will rise in level even before local agricultural drainage has commenced.
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• The actual volumes of flow in a storm event in an urban area may increase by 200% to 400% compared to volumes from a rural area. For example a 100 hectare development in the Cardinia Creek/McGregor Road system could generate annual runoff of 400 ML/annum compared to about 100 ML/annum prior to development.
Retarding basins can do little to lower such increases in flow volumes. Therefore the downstream Carrier drains must convey greater flow volumes. Unless corresponding capacity is provided in the Carrier drains the result is longer periods of medium flows in these drains.
It follows that there will be less opportunity for the Precept drains to freely empty into the Carrier drains and hence surrounding lands will be waterlogged for longer periods, even assuming levels of drain maintenance have remained constant. This only applies in few cases as most of the Carrier drains have their own outlets to the Bay, however some District landowners now pump from their property drains into both Precept and Carrier drains and this activity is dependent on the capacity of the Carriers to take the additional water without overtopping.
Under periods of extended high flows the drain banks become more saturated so more seepage into surrounding land can occur when the drains are near full. Also, slumping of steep drain banks becomes more frequent. Thus increased maintenance is required.
Within the next twenty years urban development in the Westernport catchment designated Urban Growth Zone could increase by over 9,000 hectares. The flow from this new development would be of the order of 36,000 ML/annum, compared to 9,000 ML if the area stayed rural. This increase of 27,000 ML/annum represents an increase of over 10% of the annual flows in the downstream Carrier drains and Precept drains. This further strains the downstream waterways and increases the possibility of flooding within the KLFPD. Such incremental changes need to be fully assessed and extra maintenance and augmentation works undertaken to ensure that levels of protection for District Landowners are not diminished.
It is outside the scope of this Report to fully assess the impacts of upstream urban development on the District. The issue is raised for consideration and discussion, and it is important that a full assessment of such risk be undertaken by Melbourne Water. It could well be that extra funding needs to be made available from Council and Melbourne Water rates to preserve past drainage performance standards by upgrading of both Carrier and Precept drain flow capacity. It is also outside the scope of this Report to assess the full range of mitigation options - but one option that has been proposed is the excavation of the virgin ground between the channels within the main levee banks on the Carrier drain systems of Cardinia, Toomuc and Deep Creeks.
A further issue which may impact on drain flow capacity is climate change. While again outside the scope of this Report it is apparent that any rises in sea level or increased frequency of high intensity storms would put further pressure on all the KLFPD drains through increased tailwater inundation at the lower ends.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
3 The Dalmore Road Drain Catchment
3.1 Drainage area and land uses
The Dalmore Road Drain catchment comprises an area of 1075 hectares (source Melbourne Water) from Cardinia Road in the north to the outlet at Westernport Bay. The catchment is long and narrow, and the Drain length is about 8.3 km, from Cardinia to the South Gippsland Highway.
Figure 3 The Dalmore Road Drain Catchment ---
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Land use in the catchment is primarily agricultural and includes stock grazing, vegetable growing and cereal crops. There has only been very limited new development in this catchment with a few new residences around the Cardinia township and new farm buildings such as packing sheds.
Annual flows from the catchment will vary depending on catchment wetness and storm intensities. If an average Co-efficient of Runoff of 0.3 is adopted then annual discharge would be 2580 Ml/annum. For a single storm event of 100 mm of rainfall over 24 hours the co-efficient of Runoff could be as high as 0.5 and the event discharge would be 538 ML.
Peak flows from the catchment can be estimated by use of the Rational formula. Ten year and 100 year Average Recurrence Interval (ARI) flows for the Dalmore Road Drain catchment are accordingly estimated to be 9 m3/s and 22 m3/s respectively.
Melbourne Water (2012) has provided estimates of ARI flows from the 1075 ha Dalmore Road Drain catchment as follows:
1 in 100 ARI = 30 m3/s 1 in 50 ARI = 22 m3/s 1 in 20 ARI = 15 m3/s 1 in 10 ARI = 10 m3/s 1 in 5 ARI = 7.5 m3/s 1 in 1 ARI = 3.0 m3/s
These are not estimates of the flow capacity of the Dalmore Road drain which prior to the recent June 2012 flood event probably had a capacity of less than a 1 in 1 ARI. This is discussed further in the following section.
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4. Capacity and Condition of Dalmore Road Drain
4.1 Factors Effecting Theoretical Flow Capacity
It is understood that the performance of the Dalmore Road drain and its tributaries has been a matter of concern to Landowners for many years. Most recently, on the 13/6/12, a District Landowner meeting was held in Koo Wee Rup and Melbourne Water was advised of a number of problems including inadequate maintenance and excessive vegetation in the drain downstream of the floodgate, and poor opening capacity of the floodgate.
The recent June 2012 storm event again highlighted the incapacity of the Dalmore Road Drain to effectively drain its contributing catchment within a reasonable period of time so that pastures and crops are not adversely affected by surface water inundation. As for any drain, the flow conveyance capacity of the Dalmore Road Drain is dependent on a number of factors. These are:
1. The hydraulic radius of the channel in meters, which is defined as the ratio of its cross- sectional area to its wetted perimeter (the part of the cross-section, bed and banks, which is in contact with the water). Thus the greater the hydraulic radius, the greater the efficiency of the channel and the less likely the drain is to flood. The highest values occur when channels are deep, narrow, and semi-circular in shape.
2. Manning's roughness coefficient “n” is the accepted measure which represents the resistance to flood flows in channels and flood plains. The results of Manning's formula, an indirect computation of stream flow, have applications in flood-plain management, flood insurance studies, and in the design of bridges and highways across flood plains.
3. Slope of energy grade line (Se) in meters per meter. This represents head loss per length of drain. For uniform steady flows, the energy grade line can be taken as equivalent to the slope of the water surface, and equivalent to the slope of the bottom of the drain.
For all practical purposes in this Report what is important is that the velocity of flow, and hence total volume of water conveyed per unit time in Dalmore Road Drain, would decrease with:
• Decrease in cross sectional area (eg through a narrower and shallower channel containing sediment). Surveys of the Drain (see below) show that between 2007 and 2012 about 0.4 m of silt had accumulated on the bed and banks of the lower reach of the Dalmore Road Drain. This would effectively lower the cross sectional area of the Drain. • Decrease in bed slope (eg through a higher level point of discharge, again because of sedimentation). The Dalmore Road Drain has a very low bed slope going from Australian Height Datum (AHD) of 0.0 metre (mean tide level) at the South Gippsland Highway to 4m AHD at Cardinia. This represents an average bed slope of 0.0005 m/m (compared with 0.0012 m/m for Bunyip River from Iona to Westernport Bay). This is an extremely low bed slope so velocities in the Dalmore Road Drain will be relatively low; consequently there must be increased emphasis on maintaining a clean, wide channel.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
• Increase in the roughness of coefficient (eg by growth of vegetation on the bed and banks of the channel). It is estimated that the average Manning’s n over the length of the channel was 0.065. With adequate maintenance 0.045 could easily be achieved.
The combined effect of the changes in roughness (Manning’s n) and cross section, (little can be done about the average bed slope), could be examined by considering theoretical trapezoidal channels, of dimensions as shown in the table below which are very similar to the dimensions of the Dalmore Road at Cross Section 7 of the survey which was carried out in 2012.
Table 7 Estimates of theoretical flow velocity under various drain conditions Drain Condition Drain Morphology Velocity Estimated (assume bed slope=0.0005 m/s Flow m3/s m/m) 1.Drain in silted condition with mangroves Trapezoidal channel of 10 0.28 2.2 at toe of drain (eg drain as in condition at metre top width, 1 metre bed June 2012 flood) n=0.065 width and 1.4 m to base 2. Drain if only mangroves removed, no Trapezoidal channel of 10 0.41 3.1 silt removed. n=0.045 metre top width, 1 metre bed width and 1.4 m to base 3. Drain if bed and one bank de-silted thus Trapezoidal channel of 10 0.40 3.8 removing mangroves from bed and one metre top width, 2 metre bed side (eg as in works done post June 2012 width and 1.7 m to base flood). Mean n= 0.05 4. If bed and both banks de-silted and all Trapezoidal channel of 10 0.46 4.7 mangroves removed. n=0.045 metre top width, 1 metre bed width and 1.7 m to base
It can be seen that drain maintenance would theoretically double the flow capacity of the Dalmore Road Drain. Observations after the June 2012 storm however indicated that even 2.2 m3/s may not have been achieved due to more serious capacity reduction in the 650 metre section of Dalmore Road Drain immediately upstream of the South Gippsland Highway. This section was not included in the 2012 survey but, it is the view of local Landowners that sedimentation and obstruction by recent vegetation growth in this section is a major causative factor in flow reduction.
4.2 Dalmore Road Drain Surveys
Surveys of the Dalmore Road Drain, in the tidal section downstream of the Dalmore rd floodgate, were completed by SMEC Urban in February 2007 and again in April 2012. The surveys plot the dimensions and depth of the drain at specific points, known as Cross Sections. The depth measurements use Australian Height Data (AHD) as the reference point. AHD is the base height adopted nationally, and approximates mean tide level. Figure 4 below compares equivalent Cross Sections from the two relevant surveys.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
Figure 4 Cross Sections Comparisons between 2007 and 2012
It can be seen from Figure 4 which provides data at Cross Sections 7 and 9 (from 2012 survey) and equivalent Cross Sections 15 and 16 (from 2007 survey), that there has been considerable deposition in the drain over the five years. The survey results have also been tabled below (Table 8) for ease of comparison.
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Table 8 Comparison of 2007 and 2012 Dalmore Road Drain Survey Results
2007 Survey 2012 Survey Cross Section Distance(metres) Bed Level m Cross Section Distance(metres) Bed Level m Number upstream South AHD Number upstream South AHD Gippsland Hwy Gippsland Hwy 1 -660 (downstream) -0.26 2 -460 -0.67 3 -28 -0.29 4 -60 -0.37 5 Between bridges -0.50 6 Between bridges -0.41 7 0 -0.15 8 40 0.04 9 160 -0.2 10 260 -0.1 11 340 0.02 12 570 -0.15 1 650 0.39 2 715 0.17 13 700 -0.07 3 785 0.24 4 875 0.53 14 950 0.47 5 950 0.56 6 1050 0.52 15 1120 0.30 7 1120 0.63 8 1230 0.65 16 1330 0.53 9 1330 0.68 17 1550 0.50
It can be seen from the above table that in the 2007 survey there was a distinct rise in bed level of 0.5 m between section 13 and Section 14 with only minor further rise by Section 17. The average rise over sections 12 to 17 was 0.26 m.
It would seem that over the next 5 years siltation continued both upstream and downstream of Cross Section thirteen. By 2012 the average bed level in the equivalent sections 1 to 9 was 0.49 m AHD. Thus about 0.23 m of silt had been added. Given that there was already an average at least 0.37 m of silt in 2007, then there was at least 0.6 m of silt in the bed in 2012.
Melbourne Water have advised that their assessment of the 2007 Survey report stated that removal of the mangroves would not significantly reduce the area of local inundation, concluding that removal would result in a reduction of only 50mm around Cross Section 12, and that sediment removal would give a 40 mm reduction. However their report did not look at the actual capacity of the Dalmore Road Drain, only on theoretical total flows. Their report was also within the context of no mangrove removal or de-silting at, and just upstream, of the South Gippsland Highway so free outfall was not applied. Their report recommended that works be undertaken to regrade the channel to facilitate the free draining of flows and reduce the area of inundation to the east. While the Melbourne Water report considered flooding in terms of area it
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains did not refer to the important issue of duration of inundation. Works were not undertaken at the time.
It is the view of the present study that the effect of mangrove and silt cleanout, from immediately downstream of the South Gippsland Highway (SGH) to the present floodgates, would in fact be of very substantial improvement in performance of the Dalmore Road Drain. The greatest benefit would be seen in reduction in the period of land inundation in a flood event. For example, it is estimated that the June 2012 storm resulted in a runoff volume of 430 Ml (430,000 m3) and a peak flow of 9 m3/s. At an average flow of about 2m3/s for 75% outflow time the total drainage time should be of the order of 3.3 days after cessation of rainfall. However average flows may well have been actually less than 1 m3/s, so markedly increasing the period of outflow and consequently prolonging the period of Dalmore District land inundation.
Unfortunately the 2012 survey did not commence at the South Gippsland Highway but rather a point approximately 650 metres upstream. Thus data is not provided on a critical section of deposition in the Dalmore Road Drain which, in the opinion of local Landowners, is critically important.
4.3 The Floodgates on Dalmore Road Drain
A further factor influencing flood flow conveyance is the performance and siting of any tidal floodgates on the system. The present floodgates on the Dalmore Road Drain (see photo 3 and 4), located some 1330 m upstream of the South Gippsland Highway, are relatively heavy structures which can impede outflows. The gates dimensions are 183 cm wide by 153 cm high giving a cross sectional flow area of 2.8 m2, compared to the channel cross section of about 10 m2 upstream and downstream. This limited cross section and the heavy gates would significantly retard outflows. Photo 3 demonstrates this retarding effect by reference to the difference in water level from upstream to downstream.
The floodgates would in this respect be better placed further downstream at the South Gippsland Highway, as are the floodgates of the Cardinia Catch Drain (Photo 5). This would have five significant effects:
1. It would increase the duration of freshwater outflow as the saltwater inflow on each rising tide into some 1300 m of the Dalmore Road Drain between the South Gippsland Highway and the present floodgates would not have to first flow out after every high tide, so improving drainage capacity. 2. It would limit tidal intrusion such that the drain would then remain as a freshwater system. 3. Sediment deposition would be much reduced as there would be far less flocculation of fine particles in freshwater. 4. There would be reduced opportunity for input of sediment derived from re-suspension in the Bay. 5. Mangroves would not grow prolifically in the freshwater, so eliminating any need for future removal.
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
4.4 Possible Sources of Drain Sediment
Between the 2007 survey and the 2012 survey there was an average of 0.23 m of silt added to the bed of the Dalmore Road Drain. This is estimated to amount to 1500 m3 of silt per km of drain. This is a large amount and seriously impacts on drain performance. There are two potential sources of such sediment:
1. Sediment generated from catchment land surfaces 2. Landward transport of fine sediment from the Bay
Observations around the Dalmore Road Drain catchment indicate that while some catchment derived sediment comes from road wash-off, most is generated in runoff where “lands” are placed very close to property drains and as a result sediment is easily transported through to the larger Precept drains.
There may need to be more locally-based attention of district Landowners to best practice for retention of sediment and nutrients on their properties. For example narrow grass swales and offset buffers would be very effective in trapping such pollutants. However such measures are rarely seen in the District. It is said that grass swales could harbour thrips and other insect pests which could jeopardize export of produce. This may explain the minimal use of grass swales to date. Any stormwater best management practice solutions in the area would need to be soundly based and not result in additional problems for Landowners.
It is possible that a major proportion of the sediment deposition now comes from re-suspension of fine sediment in the mudflats adjacent to Lyalls Inlet, which is carried up into the Dalmore Road Drain during incoming tides, and subsequent deposition in the Drain. Marsden et al (1974) note that tidal energy rather than freshwater inflow provides the drive for most sediment movement in Westernport Bay including the tidal inlets, especially at Spring tides.
Photo 3 Dalmore Road Drain at Floodgates (23/6/12)
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Photo 4 Dalmore Road Drain downstream of Floodgate 20/7/12 (upper right)
Photo 5 Cardinia Catch Drain Floodgates at South Gippsland Highway
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5. Observation Following June 2012 Storm Event
The Kooweerup rain gauge recorded a total of 132.4 mm for June 2012. On the 21/6/2012, 18.2 mm of rainfall was recorded and 62.0 mm the following day. There had been significant rainfall earlier in the month (28.0 mm recorded on 4/6/2012 and 12.2 mm on 5/6/2012).
These results are similar to rainfall recorded at Dalmore (courtesy of Mrs Judy Rayner) of 132.5 mm for June, with 16.0mm on the 21 June and 56 mm on the 22 June. While such rainfalls are high, they are not unusual, and rainfall records indicate that such rainfalls can occur two or three times a decade.
Kooweerup mean rainfall is 783 mm/annum and median rainfall is 802 mm /annum. This can be compared to 930.4 for 2010 and 907.6 for 2011. For 2012 the total rainfall to the end of June was 534 mm compared to a historical mean of 342 mm to end of June. Historical monthly rainfalls for Kooweerup and Cranbourne are shown in Appendix 1.
Any assessment of storm event impacts must take into account prior rainfall events as these will result in different soil conditions and runoff rates for equivalent rainfalls. As a result of the high rainfall in previous weeks the Dalmore district soils were still quite moist when the second event for June 2012 occurred. Therefore infiltration was reduced and the resulting runoff was more equivalent to an estimated 1 in 15 year ARI flows, rather than an estimated 1 in 7 year ARI flows that would have resulted in drier conditions.
In the June 2012 event, the period of inundation would have been somewhat higher than normal even in a clean Dalmore Road Drain situation as the ground was wet, and return to low flow conditions would be delayed by the relatively slow rate of infiltration through the District soils and into the private and public drains.
Concurrent observations in nearby Devon Meadows which was a similarly wet catchment at the time, and which received a total of 69.6 mm for the two days showed that drain flows rose and fell quickly, and flooding at road crossings and adjacent land had disappeared within 24 hours of cessation of rainfall, except in instances where the downstream drains were clearly in-filled by sediment or otherwise blocked. Such comparison must be treated cautiously as the bed slopes in the Devon Meadows waterways are far higher than in the Dalmore Road Drain.
The June 2012 storm event did not lead to very high flows in the Bunyip Main Drain, as upper catchment rainfalls were comparatively low. A peak of 76.4 m3/s was recorded at the Iona gauge at 6pm on 22/6/12 and had dropped to 26 m3/s by the 24/6/12. Flooding of the South Gippsland Highway near the Bunyip Main drain was not due to flows from the Bunyip Main Drain, rather it was caused by overflows from the Southern Boundary Drain, downstream of Koo Wee Rup.
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5.1 Dalmore Road Drain Condition and Levels
Inspections of the Dalmore Road Drain were conducted on the 26/6/12 and 30/6/12, 2012.
The inspection of 26/6/12, four days after the major rainfall event, was conducted while the Drain levels were still very high and generally within 30 cm of the top of the Drain bank. At this time large areas of adjacent farmland still carried surface water and Drain levels were still high (photos 6 and 7). Even at these high levels the presence of in-stream growths of emergent aquatic plants (mainly Phragmites sp.) was apparent. Larger woody plants were not observed within the Drain bed or banks except downstream of the floodgate structure where mangrove growth was more prolific along the banks.
During the inspections a number of Landowners voiced their concern that levels in the Drain had not dropped. There were similar concerns expressed about the levels in Tooradin Inlet Drain. Given the elapse of 4 days since the last significant rainfall this concern was justified and observations confirmed that flow velocity was very low, at an estimated 0.1 m/second. It was concluded that flow rate and velocity was being limited by growths in the Drain and sedimentation of the bed, especially in the reach from the Dalmore Road floodgate to the South Gippsland Highway, and by deduction, further downstream in the Bay. The restriction of flows through the floodgate was also a potential factor along with high tides creating high tailwater conditions in the Drain downstream of the floodgates.
By the 30/6/12 the Dalmore Road Drain level was much lower than previously and nearly all of the adjacent lands had drained of surface water. It was noted that a Melbourne Water excavator had been increasing the drainage capacity in the reach below the floodgates to a point approximately 400 metres from the South Gippsland Highway.
In summary this storm event occurred at a time when soil moisture levels were high, infiltration capacity was low and the Drain performance was in all likelihood significantly compromised by sediment and vegetation. Hence impacts on property and crops were high.
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Photo 6 Flooding of Asparagus Crops at Railway Rd, Dalmore 25/6/12
Photo 7 Farmland flooding along Dalmore Road 26/6/12
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5.2 The Diversion to Cardinia Catch Drain
On the morning of 26/6/12, in a response to the emergency situation on many properties facing potential losses of high value asparagus crops, a diversion was placed in the Dalmore Road Drain (M. Baillieu, pers.com., see photo 8). Melbourne Water permission for such diversion was not obtained. In normal circumstances is it imperative that only Melbourne Water undertake works on drain bed and banks at their technical discretion.
The diversion was constructed by excavation of a 3 metre portion of the east bank of the Dalmore Road Drain just upstream of the tidal floodgate. The water spilling out of this diversion flowed to the east for about 1.6 km in a previously constructed private drain within the Gowan Lea Farm property and finally spilled into the Cardinia Catch Drain (Photo 9). This diversion was inspected on the afternoon of 26/6/12 and a number of observations were made in relation to this diversion:
• The diverted flow in the Gowan Lea Farm drain was estimated at 1 m3/s. This compared to an estimated flow downstream in the Dalmore Road Drain of about 0.3 m3/s. It was also noted that the left bank of the Dalmore Road drain (looking downstream from the floodgate) had been topped with fill from a recently constructed Gowan Lea Farm drain. This fill raised the left bank of the Dalmore Road Drain but did not significantly intrude into the banks of the Drain or lower its cross sectional area. • At the eastern outlet of the Gowan Lea Farm drain into the Cardinia Catch Drain a few metres of a private levee had been lowered and the water flow into the Cardinia Catch Drain was completely unimpeded. It was evident that levels in the Cardinia Catch Drain were lower than levels in the Dalmore Road Drain. Property survey plans show that land levels (heights above mean sea level) at both drains are virtually the same. • There was a strong outflow at the mouth of the Cardinia Catch Drain through the tidal floodgates immediately downstream of the South Gippsland Highway. At this time the Dalmore Road Drain channel downstream of the South Gippsland Highway had a very small flow and by reference to tide height the bed level of the Dalmore Road Drain was estimated to be about 1.5 metres higher than the bed level of the Cardinia Catch Drain. • The Dalmore Road Drain level at Gowan Lea Road had dropped by about 400 mm since the morning as a consequence of diverting the flow through Gowan Lea Farm to the Cardinia Catch Drain.
The above observations would seemingly support the contention by local Landowners that maintenance in the Dalmore Road Drain was urgently required. Such contention is supported by the results of the 2007 and 2012 drain surveys discussed earlier. The fact that water could drain well though one drain and not another would indicate that the Dalmore Road Drain was not performing to past expectations or standards. It was concluded that this was due to:
• Sedimentation and consequent increase in bed level around the South Gippsland Highway, thus reducing the bed slope and capacity in the drain. • Sedimentation and growth of mangroves between the South Gippsland Highway and the Dalmore Road tidal floodgates, reducing cross sectional area of the Drain and increasing channel roughness.
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• Sedimentation and growth of emergent aquatic plants in the bed of the channel upstream of the tidal floodgates to Manks Road. • Limitation of flows through the Dalmore Road floodgate due to design characteristics and limited cross sectional area. • High tides creating tailwater conditions in the Drain that impeded outflows at critical times, thus decreasing flows downstream of the floodgate.
Photo 8 Diversion of drain upstream of floodgates adjacent Dalmore Road
Photo 9 Drain Diversion 100 metres west of Cardinia Catch Drain
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains
As previously noted large areas of adjacent land both upstream and downstream of Railway Road Dalmore, were still under water after 4 days. Such surface inundation persisted for some days, even after the Dalmore Road Drain had dropped in level, showing that the problem with the period of inundation is also related to property drainage and local roadside drain maintenance, as well as Dalmore Road Drain maintenance. This may be due to the fact that the need for upkeep of such local drainage was diminished during the periods of lower rainfall between 1997 and 2010. With rainfall and flows back to levels seen prior to those years, any deficiencies in the Landowner drainage systems become readily apparent.
In response to the June 2012 flood Melbourne Water commenced “emergency” cleanout works on 26 June on the bed and right bank of the Dalmore Road Drain, downstream of the Dalmore Road floodgate. Photos 10 and 11 show the before and after condition of the drain.
Photo 10 Dalmore Road Drain on 26/6/12 looking downstream from Dalmore Road prior to July 2012 de-silting work
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Photo 11 Dalmore Road Drain after July 2012 de-silting of bed and right bank (looking downstream from Dalmore Road)
The drain upstream of the floodgates still has considerable emergent aquatic plant growth in places (photo 12)
Photo 12 Dalmore Rd Drain upstream of floodgate (27/08/12)
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6 Potential Strategies to Improve Drainage
Improvement strategies can be implemented at all scales from property drainage to major catchment drainage. In addition there can be overarching policies and strategies which will be applied throughout the District.
6.1 Drainage Improvements by Landowners.
Under current rainfall patterns there are far higher levels of soil moisture than previously, resulting in saturation to near the surface. In a storm event the total soil horizon can quickly become saturated especially if surface flow also moves onto the land through overbank flow or seepage from drains. Once saturated, the draining of the soil profile can vary from hours to days. Water movement through soils can be very slow, particularly in the absence of a system of underground drainage. If local receiving drains are high and surface water also persists, the process of drainage of the soil profile will be further delayed and crop loss made more likely.
Landowners can help themselves by ensuring their own property drains are adequate to remove surface water on their property. This may include all forms of surface and subsurface drainage. There is some consequent effect to this as the more efficient the property drainage, the quicker the flows reach the District drains, hence the increased risk of overtopping in a flood event unless additional capacity is provided.
As previously noted, Landowners could protect downstream drains from siltation by trapping any generated sediment on their own land. This could be by larger setbacks of cultivated areas from drains, aided by use of grassed swales and silt traps.
6.2 Drainage Improvements by Councils.
There is still plenty of scope to improve the system of roadside drains and associated infrastructure such as small floodgates and culverts managed by Councils. It is outside the scope of this Report to specifically identify such works however district Landowners and Melbourne Water should request that the City of Casey and the Shire of Cardinia undertake a review of the condition and performance of local drains, not managed by Melbourne Water, and outside the control of Landowners.
6.3 Drainage Improvements by Melbourne Water
6.3.1 Improve Drainage Capacity of Dalmore Road Drain and other Precept Drains
The previous discussion would indicate that the following measures could be considered by Melbourne Water to increase the flow conveyance capacity of the Dalmore Road Drain and so reduce flood impacts on District lands:
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1. Cleanout the Drain bed above the South Gippsland Highway so the bed level is similar to that of the Cardinia Catch Drain. If the bed below the South Gippsland Highway is sedimented, consideration should also be given to its removal.
2. Relocate the existing Dalmore Road tidal floodgate to a position just upstream of the South Gippsland Highway. This would give extra freshwater outflow time on each tidal cycle and reduce sedimentation.
3. Provide maintenance to the floodgates or augment the capacity of the floodgates to a 10 year ARI flow
4. De-silt and lower the bed level all the way from South Gippsland Highway to Dalmore Rd – this will include removal of mangroves which have grown in the Drain over recent years.
5. In consultation with landowners, consider diversion of Dalmore Drain flood flows to the Cardinia Catch Drain, in the reach from Manks Road to the Railway. Cleanout of the lower Dalmore Rd Drain would still be required.
6. Cleanout aquatic plant growth from Dalmore Road Drain upstream to Manks Road
Subject to Melbourne Water assessment and input from the KPLFD Advisory Committee, similar maintenance works may prove to be required on drains such as the Tooradin Inlet drain and other District drains.
6.3.2 Prepare 5 year plans for Carrier Drain and Precept Drain Maintenance
These must be based on assessment of required level of protection of each drain, drain cross section, and drain flow capacity, both when cleaned and before the next scheduled maintenance. The plans should also include regular inspection and maintenance of all major floodgates.
It is essential that the greater part of Precept rate collected in the KLFPD be spent on the Precept drains according to an agreed formula as discussed in Sections 2.3.4 and 2.3.5. The Melbourne Water general drainage rate revenue should be the primary source for expenditure on Carrier drain maintenance and capital works, in the same way that Melbourne Water uses general waterways and drainage revenue for capital works and maintenance on other waterways in its area such as the Dandenong Creek, the Yarra River, the Bass River, or the Maribyrnong River.
6.4 Clarification of Regulatory Restrictions
It is understood that there has been regulatory constraint on removal of vegetation and other works on some drains in the KLFPD. In particular the application of provisions in Environment Protection and Biodiversity Conservation Act 1999 (the EPBC Act) has resulted in cessation or postponement of maintenance or other works.
The EPBC Act is the Australian Government’s central piece of environmental legislation. The EPBC Act comes into play when a proposal has the potential to have a significant impact on a
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains matter of national environmental significance. The eight matters of national environmental significance to which the EPBC Act applies are:
1. world heritage sites 2. national heritage places 3. wetlands of international importance (often called ‘Ramsar’ wetlands after the international treaty under which such wetlands are listed) 4. nationally threatened species and ecological communities 5. migratory species 6. Commonwealth marine areas 7. the Great Barrier Reef Marine Park 8. nuclear actions.
Of these eight matters the two of key relevance to the District are the two referring to the Ramsar wetland of Westernport and nationally threatened species and communities.
Any actions which can threaten species or wetlands of national importance are termed “Controlled actions”. In the case of the Bunyip Main Drain works (the aim of which was to upgrade flow between the 11 and 13 Mile Roads from 150 m3/s to 210 m3/s), a report by Melbourne Water (Waterway Alliance) dated 10/6/2011 concluded that the proposed action was not a controlled action with regard to potential impacts on any endangered species, such as the Southern Brown Bandicoot, the Australian Grayling, the growling Grass Frog and the Eastern Dwarf Galaxias. Subsequently on 14 July 2013 a referral decision was made and the Federal government decided that it was a controlled action and assessment and approval would be required before proceeding.
Similarly there have been restrictions on cleanout of the lower Dalmore Road Drain as it is considered as part of the Ramsar wetland and white mangrove growth in the lower drain is seen to provide ecological diversity and habitat. The Mangrove Shrubland Ecological Vegetation Class (EVC) is widespread; it is increasing around Westernport Bay, lining 40% of its coastline; and its Conservation Status is of least concern in Gippsland Plains Bioregion (DSE website).
Whether the vegetation is native as in mangroves, or exotic as in Spartina, or whether it provides habitat for native animals, is not the issue in question. The issue is that past decisions and State and Federal policy changes effectively restricting maintenance have been made, on which peoples’ livelihoods depend, often by people geographically removed from the District and unaware of the unique and complex nature of the essential drainage infrastructure built up over several generations. Decisions which impact on the livelihood of District Landowners should not be made without prior consultation and agreement with them. Melbourne Water needs to be active in ensuring that the constructed drains are excluded from policy changes in the first instance, rather than in obtaining special approvals for works after the changes.
The outlet for the Dalmore Road Drain had until more recent years, been free of blocking mangrove growth and sediment build-up, and it should be so maintained. It is incomprehensible that the regular cleanout of a drain that has been in place and serving the District for generations can be defined as a “proposal” and be subject to conditions of the Act. If that were the case then every act of roadside verge maintenance, council reserve mowing, council drain maintenance, freeway verge maintenance, council or property maintenance in the Westernport catchment
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Drainage Capacity of Dalmore Road Drain and KLFPD Drains could become a “controlled act” as it could potentially affect threatened animal and plant species.
If a real need is established for retention and re-establishment of mangroves over and above the large areas that line the north-western sectors of Westernport Bay, then the Dalmore Road Drain should be enlarged to an extent such that flow conveyance is adequate even with mangroves lining the channel banks, or allow for controlled flood flow break out as would have occurred naturally in the past.
Melbourne Water has acknowledged that it has an interest and obligation “ to provide improved environmental outcomes for drains and waterways within the KLFPD where this does not compromise the drainage and flood protection functionality of the drains” (from brochure dated 31/5/11 describing proposed weed control and habitat creation on a number of district drains). While all native vegetation has some value, it is also true that the system of drains in the District was constructed many years ago for the specific purpose of providing drainage, and for flood protection, so that farming activities could be undertaken. As for any farming activity, the aim is not just to survive but to prosper. Even basic survival will not be possible if the outlets to the Districts drains are blocked with sediment and vegetation.
Given the history of the District there is a view that it is not reasonable to contend that protection of bandicoots or growling grass frogs or other species should extend to constructed drains which are essential for protection of property, livelihood and, potentially, peoples’ lives. Similarly, the lower drains should not be seen to be part of the Ramsar Wetland of Westernport Bay. This issue needs to be resolved at an early stage.
6.5 Summary of Problems and Potential Responses
The following Table 9 summarises issues and problems identified in this Report and suggests some potential responses. It does not claim to identify the only responses available. Many of the responses will involve Melbourne Water as the drainage and waterway manager for the District. Some responses could be implemented quickly while others may take longer as either significant further investigation or extensive works are involved. Melbourne Water may, after consideration and investigation, accept, reject, or modify the suggested potential responses.
It may also in consultation with the KLFPD Advisory Committee and others identify further or more effective responses. Improved communication between all parties will be required and Melbourne Water has recently demonstrated its willingness to both participate in and where necessary facilitate appropriate means of consultation and communication.
The primary purpose of Table 9 is to obtain acknowledgement of present problems and then find solutions which are socially, economically and environmentally appropriate, and which will ensure the ongoing sustainability of the District as a major producer of fresh food and farm products.
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Table 9 Summary of Problems/Risks and Potential Responses Scale/Type Perceived Problems/Risks Potential Responses (Structural and Non Structural ) Council and • Lack of free flow into Precept • Council to work with Landowners to identify Private drains system shortfalls and rectification measures. Drains • Lack of adequate floodgating to • Adoption of best management practices for prevent saltwater backflow sediment mitigation • Lack of subsoil drainage • Sediment generation from farmland Dalmore Rd • Restricted flow conveyance due to • De-silt drain and remove bed and bank Drain vegetation growth resulting in vegetation over whole length to SGH. overtopping of Drain, increase in • Relocate flood gate downstream to SGH. area of inundation and increase in • Investigate and augment floodgate capacity duration of inundation • Investigate storm flow diversions to Cardinia • Restricted flow conveyance due to Catch Drain between Manks Road and the siltation and vegetation growth of Railway. lower reaches near the bay Other • As for Dalmore Road Drain above. • Inspection and if necessary survey of all Precept drains required to record and ascertain current capacity. Drains Carrier • Flow capacity problems due to • Restrict all woody vegetation only to the top Drains vegetation growth or sediment of bank and outer bank areas. accumulation. • Inspection and if necessary survey of all • Higher volumes of flow from drains required to record and ascertain current upstream urban development. capacity. • Consider removal of virgin soil between main levees to increase Carrier drain capacity. • Investigate magnitude of impact of upstream development and if necessary seek financial assistance from councils to mitigate impacts • Construct a new channel from hills to Bay which can be formed and naturalized as a high ecological value waterway and wildlife corridor. District and • Higher tides • Investigate and predict potential changes in system wide • Potential sea level rise frequency and extent of future inundation due to sea level rise and identify response –planning measures.
District • Poor understanding of level of • Education of landowners on flood risk and wide protection and level of service levels of flood protection currently provided. education provided • Consultation and agreement with landowners • Tendency to treat drains as on levels of flood protection they pay for and and environmental assets rather than level provided. consultation drainage infrastructure assets • Seek legal advice as to applicability of EPBC • Gaps in Landowner involvement Act. Seek to class District drains as civil and consultation in Melbourne assets which do not fall under the ambit of the Water decision making. EPBC Act • Past failure to spend major • Expand the consultative role of the KLFPD proportion of precept rate collected Advisory committee so that all district on precept drains. ratepayers feel represented. • Form one or more District associations covering main areas within the district.
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REFERENCES
Brizga, S & Associates Pty Ltd, Pat Condina and Associates, Neil M. Craigie Pty Ltd, Lawson and Treloar Pty Ltd and Ecology Australia Pty Ltd. (2002). Northern Waterways of Western Port. Geomorphological and Water Quality Management Study (Incorporating Floodplain Re- engagement Feasibility Assessment). Report for Melbourne Water.
Cardno (2012) 2011 Storm at Koo Wee Rup Flood Investigation Prepared for Melbourne Water February 2012
Pat Condina & Associates, Neil M Craigie Pty Ltd, S. Brizga & Associates Pty Ltd, Aquatic Systems Management Pty Ltd (2005) Review of Urban Stormwater Contaminant Impacts on the Streams and Marine Environment of Western Port and Catchment Report prepared for Department of Sustainability and Environment
East LR (1935) Swamp Reclamation in Victoria Journal of the Institution of Engineers, Australia Vol 7, No.3 March 1935
Marsden M. A. H. and Mallett C. W. (1974) Morphology and Sediment Distribution, Westernport Bay, Victoria, report to Westernport Bay Environmental Study.
Melbourne Water (1995) Internal Memorandum, dated 19 June 1995
Melbourne Water (1998) Discussion Paper Bunyip Main Drain Investigation Report prepared by Waterways and Drainage, February 1998
Melbourne Water (2001) Bunyip Main Drain Rehabilitation Project Information Bulletin No. 3 April 2001.
Ritchie E. G. (1937) Proposed Works for Alleviation of Flooding in the Koo Wee Rup District. Report presented to both houses of Parliament, Victoria
Roberts, D. (1985) From Swampland to Farmland Rural Water Commission Victoria
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Appendix 2 Melbourne Water Community Newsletter Reprinted courtesy of Melbourne Water
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Pat Condina & Associates August 2012 50 Re: Inquiry into Rural Drainage in Victoria - Submission by Cardinia Shire Council Ivan Zwart to: Paul Richardson 07/01/2013 01:12 PM Cc: Gregory Gardiner, Karen Taylor
Hi Paul,
Thank you for your submission, we'll be in touch if we need anything further.
Cheers Ivan
Ivan Zwart | Research Officer Environment and Natural Resources Committee | Parliament of Victoria
A: Parliament House, Spring Street, East Melbourne 3002 T: (03) 8682 2806 | F: (03) 8682 2818 E: [email protected] W: www.parliament.vic.gov.au/enrc @VicParliament @VicParlCtees
Paul Richardson Dear Mr Gardiner, Attached is Cardinia Shire... 21/12/2012 04:39:53 PM
From: Paul Richardson
Dear Mr Gardiner,
Attached is Cardinia Shire Council’s submission to the above subject.
Regards
Paul Richardson | Manager Assets & Development | Cardinia Shire Council Ph: 5945 4317 | Mob: 0418 317 375 | Fax: 5941 3784 Email: [email protected] | Web: www.cardinia.vic.gov.au PO Box 7 Pakenham VIC 3810 | Customer Service: 1300 787 624
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Cardinia Shire Council has implemented anti-virus software, and while all care is taken, it is the recipient's responsibility to ensure that any attachments are scanned for viruses prior to use. Cardinia Shire Council monitors its email traffic.[attachment "Inquiry into Rural Drainage in Victoria - Submission - 21 December 2012.pdf" deleted by Ivan Zwart/ParlOfficer/PARL] [attachment "Dalmore Road Drain Report Final 210812 (2).pdf" deleted by Ivan Zwart/ParlOfficer/PARL]