Hardys Bay

to

Hardys Mangrove Swamp

a quick transition by

Sedimentation

Researched and written by

Graeme Smith

Address    46 Pretty Beach Road

                Pretty Beach  NSW 2257

Phone     Day 0243234350

             Night 0243602622

Fax                 0243231773

Email abroboard@bigpond.com

Oct 03 Rev1

Introduction

 Death by sedimentation has been an all to familiar occurrence for many of Australia’s coastline waterways. It’s a problem that has become it seems, too hard to take action against because of the number of local and state run government departments that are involved in such action. Departments such as Fisheries, Waterways, Infrastructure Planning, and Natural Resources and the relevant local councils all have some degree of authority over our waterways and tributaries. Over zealous environmental groups  are another factor to contend with, and despite their passion and concern, often lack the knowledge to thoroughly assess the projects in which they become involved.

Common sense solutions it seems now avoid us, and huge quantities of money must first be spent on environmental impact studies before a single shovel load of sediment can be removed from our waterways.

We must accept the fact that all bays are subject to natural sedimentation which in most cases has been accelerated by human activity. Sedimentation by any means spells the beginning of the end to any waterway and the only antidote for those areas now badly affected is sediment removal.

Its an alarming situation considering Australians love the water, that we will quickly allocate millions of dollars to rectify a single roundabout that is causing traffic delays, yet nothing is allocated to removing the silt that continues to build up in our soon to be, not so beautiful or useable waterways.

We have the technology to restore sediment effected waterways and reduce future sedimentation, and we have a responsibility to future generations to take action now to rectify degraded waterways.

Our future generations have a right to be able to enjoy our waterways the way we do today, so we must not allow bureaucratic complexity to blind our vision of what can be done or what should be done.

Hardys Bay – the early 1900’s

The Central Coast has its share of treasured waterways and more than its share of sedimentation problems within the Brisbane Waters system. Hardys Bay in the lower region of Brisbane Waters is a classic case where excessive sedimentation is responsible for the loss of a large proportion of the pristine bay that was in existence pre 1900.

Plentiful fish, extensive sea grass beds, and very few people existed in the Hardys bay area around 1900. The north east corner of the bay contained a creek that ran out through small mudflats into the bay. Numerous smaller creeks drained into the bay at various other locations. Much of the bay’s shoreline was sandy particularly the western shore that in later years became the favored swimming area.

The creek in the north east corner, now known as Mudflat Creek was another good swimming spot. Swimmers using the creek constructed a diving board to use where the creek was deepest in a spot just north of the existing Noble street bridge. At low tide rowboats could be rowed up from the bay under the bridge and into the creek to about a distance of 100 metres upstream of the bridge. The creek was full of fish at high tide and occasional netting across the creek near the bridge on the outgoing tide kept the locals supplied with fresh fish.

In these early years there was a water tank works  not far south of the creek outlet owned by Joe Childs. Joe built a wooden wharf complete with sandstone landing to accommodate the ferries that were used to deliver steel and distribute his tanks, as transport by road was limited in these early years. The wharf has long since rotted away but remains of the sandstone landing can still be seen today and are officially classified as an historic site.

Mangroves that are now growing in many spots around the bay could only be found in small numbers on the higher areas of mudflats near the entrance to Mudflat creek. The rest of the bay was fringed mostly with reedy grasses. Sea grasses extended close to the shore in the north east corner and no more than 20 metres from any other shore. Soldier crabs in their thousands colonized the sandy flats surrounding the bay fringing the sea grasses.

Hardys Bay today

Fishing in the bay yields far fewer fish now days and the sea grass beds have shrunk back into the bay driven back by the ever increasing sand and sediment onslaught. Whilst the southern and western bay areas have lost considerable depth, the north eastern sector has silted up so much that floodwaters occurring during heavy rains can no longer flow easily into the bay. The floodwater backs up and causes low level flooding of the properties that back onto Mudflat creek . The creek is no longer tidal to any significant extent, in fact to call it a creek is stretching the truth as the lower section it is now better described as a sediment clogged reed infested wash way.

The swimming hole is no more, and the deep creek outlet into the bay has filled in over time with sand and road base. Mangroves of late have so infested the creek outflow that a thick carpet of mangrove roots is now forming an effective dam across the creek that cannot be breached by floodwaters. As the sediment accumulates over time the mangroves grow further and further into the bay exacerbating the situation.

These mangroves are  accelerating the sedimentation problem yet their removal is deemed as environmental destruction with heavy fines for any offenders. The proliferation of mangroves in the bay in the last 10 years or so could not have happened without the sediment build up and resultant shallower water.

Joe Childs sandstone wharf siding is fast being covered by sand mud and mangroves. The mud and sediment has accumulated to a depth of  400mm since the wharf was built. Mangroves have also taken control of the outlet of other creeks in the bay and no doubt will dam these as well, given time. Sediment tests taken by the author reveal blue metal fragments down to a depth of 450mm in shoreline locations where road base has washed into the bay. These tests confirm that the bay was deeper by at least 450mm in these locations prior to the use of blue metal on roads in the Killcare extension area.

Large patches of blue metal can be found in the bay in front of Killcare road and Blythe street also at the outlet of the Hardys Bay RSL creek. No effort by any government body has been made at any time to remove road base that has washed into the bay.

As a consequence of sediment build up in the bay, the Hardys Bay RSL creek no longer has any significant fall in the last 75 metres and therefore any bay pollution is easily trapped. Recent water samples taken from the creek in July 03 by local resident Dorothy Jenkins contained contaminates of a mixture of  black oil and diesoline. This kind of pollution is a direct result of  the high number of moored boats that have been allowed to occupy nearly all of the bay, and the lack of bilge pump out or gray water regulations for boats. 

At the local Hardys Bay slipway there is no catchment for runoff from boat maintenance operations and so the pollution from this and other similar slipways in the lower Brisbane waters, flows straight into the waterways.

How did we let it get this bad ?

 Sedimentation of Mudflat creek started to accelerate when land was cleared and roads and houses were first constructed in the Killcare extension area. Periods of heavy rain over the years washed sand, and road base (blue metal) from these unsealed roads and silt from land clearing into the natural water courses and then into the bay. Various drainage projects undertaken to by Gosford City Council to address the flooding problems have failed to arrest this sediment flow. Existing unsealed road sidings and earth gutters are still contributing to creek and bay sedimentation.

Hardys Bay parade is not sealed, and with it’s near proximity to the creek nothing stops road base runoff flowing straight into the creek and further along, into the bay.

Most of the bay shoreline is not stabilised and is subject to both tidal and rainwater erosion.

Gosford City Council has periodically removed sediment from Mudflat creek but in recent years only from the area upstream of  the Noble street bridge. Removing the creek choking mangroves from the bay side of the bridge was deemed taboo so nothing has been done to address the real cause of sediment build up and hence flooding that now grows steadily worse.

The creek depth under the Noble street bridge is so shallow that the bridge now forms a dam across the creek, and in times of high creek flow rates, forces water to back up and flood across Noble street then into the mangroves.

Gosford Council has to their credit built a sandstone block sea wall along part of Araluen drive and backfilled it with dredged sediment from the bay. The land created is now a popular foreshore park. This work was done some time ago and the sea wall now needs some attention as part of the wall is falling forward and sediment at the back of the wall in places is being washed through the gaps in the blocks then into the bay.

There has been no effort made by Gosford Council or any other government department to prevent sedimentation of Hardys Bay other than this sandstone block sea wall along Araluen drive. Other foreshore parklands and road sidings are fast eroding away into the bay.

Water pollution is another factor damaging the bay. Waterways do there best to investigate water pollution incidents but many boats have automatic battery powered bilge pumps that work intermittently, so boats with slow leaking motor sumps or leaky diesel tanks are hard to find unless someone is a witness at the time of discharge. So we have little real protection against ships of shame in Hardys Bay.

Its time for action

Its time to save Hardys bay, restore it to its former depth and ensure the relentless sedimentation is stopped. Its time to resurrect Mudflat creek and the other small tributaries that drain into the bay in such a way that their banks are stabilized and they are dredged deep enough so that low tide levels in them, and their entrances into the bay are maintained at levels too deep for mangrove growth. Salt water in the lower sections of these creeks at all times, will greatly reduce mosquito numbers in the area and help reintroduce the sea grass and fish that were part of the creeks environment pre 1900.

The entire Killcare storm water drainage system especially that part that flows into Mudflat creek must be reviewed and modified so as to minimise erosion  and sediment transportation. The installation of  sediment traps similar to those used in the Wyong shire on the Tuggerah Lakes tributaries or similar silt trap devices would help retain the silt.

There should be a general acceptance by all concerned that to maintain its depth, periodically, the bay will need an amount of silt and sand removal. This should be a routine maintenance project looked after by one authority and not subject to multi  government department involvement or interference from so called green groups that seem blind to the damage the sedimentation build up, and the resultant mangrove proliferation is doing to Mudflat creek and the other bay tributaries.

The bay foreshores must be stabilised to prevent further erosion and to clearly define the bay outline for the future maintenance of the bay.

Tidal flow into and around the bay could  be assisted by removing all of the oyster leases that are no longer worked south of the Rip bridge. The older style oyster racks and sidings are not unlike mangroves as they slow tidal flow and attract sediment build up.

Regulation regarding moored boats in the bay should be reviewed and on the spot bilge inspections made common place so as to quickly identify potential pollution risks. Many local residents are of the opinion that swing moorings in the bay should be removed and replaced by Council or Waterways administered marinas. Marinas are an efficient boat storage system and free the bay area for sailing, fishing and other recreational activities.

We don’t let cars and trucks park on our parklands or football grounds so why let boats park in our navigable waterways.

HB52

Note the dark sea grass edges in 1999 picture below compared to 1954 above and the huge advance of the sedimentation delta at the outlet of Mudflat creek.

HB53

HB55

Sea grass beds have retreated back into the bay ahead of the ever increasing sediment

delta at the outlet of Mudflat creek and the much smaller Stanley street creek.

HB54

This  1901 draft survey of Hardys bay clearly shows the deep entrance into the bay from Mudflat creek.

HB 1

The north east corner of Hardys bay 2003 now a huge sand and silt delta that in 1954 was approximately 1/5 th the size.

HB 2

A 1981 picture of Joe Childs sandstone wharf siding.

These photos show Joe Childs wharf siding in 2003 fast being consumed by silt and mangroves.

HB 24

HB 3

HB 4

HB 5

Noble Street Bridge with silt sand and road base choking what was once a deep creek.

HB 6

Mangroves choking the creek outlet not far from Noble Street Bridge.

Mangroves choke the outlet of Mudflat Creek well out into the bay.

HB 7, 8 and 9

Upstream of the bridge, the swimming hole is now a reed infested bog

approx.  300mm deep.

HB 10, 11 and 12

HB 13

Self flushing pipes feed into Mudflat Creek, but sand and blue metal clog the outlet and the spillway as seen below.

HB 14

HB 15

Some residents have stabilised the creek banks, others (as below) have not been successful.

HB 16

HB 17

This resident has taken action against the flash flooding that can and does occur in the Mudflat Creek area.  He has constructed a concrete floodwater diverting wall.

HB 18

A future area of concern.  Mangroves rapidly close off the outlet of the Hardys Bay RSL Creek.

HB 19

HB 20

Mangroves quickly take over the Mudflat Creek Delta.

HB 21

HB 22                                                                          HB 23

HB 25

A glimpse of the Hardys Bay of the future.

Rubbish trapped within mangroves at the North East corner of Hardys Bay.

HB 26

HB 27

Unsealed Hardys Bay Parade (above).  Heavy rains wash road base straight into the outlet of Mudflat Creek.

Open rubble filled unsealed drains along side Noble street feed directly into the creek (left).

HB 28

HB 29

The author find road base down to a depth of 450mm at the end of Blythe Street.

HB 30

HB 31

Blue Metal delta at the bottom of Killcare Road.

HB 32

Build up of road base material at the end of Blythe Street.

HB 33

Blue metal delta near storm water outlet opposite 46 Pretty Beach Road.

HB 34

Hardys Bay shorelines unstable and allowed to wash away into the bay.

HB 35

HB 36

Seawall maintenance, a forgotten art at Hardys Bay.

HB 37

HB 38

The creek flowing along Stanley Street cannot empty out completely because of the sedimentation and mangroves that combine to dam the creeks entry into the Bay.

Toxic algae grows in stagnant pools and will spell the end of marine life when it is flushed into the Bay in the next heavy downpour.

HB 39

HB 40

No need to ask why fish no longer thrive in Hardys Bay.

HB 41

Mudflat Creek

in times of flood becomes a

Powerful sediment pump

HB56

The power of floodwater flow has no problems carrying aggregate up to 50mm in diameter downstream to the bay.

Mudflat Creek floods - details since 1988

YEAR	DAY  /  MONTH	RAINFALL  mm	From these flood occurrence figures we can deduce that Mudflat creek needs approx. 70mm of rainfall for two successive days before the flow rate exceeds the creeks capacity and flooding of surrounding property starts. Flash flooding occurs if storms dump high rates of rainfall in short periods of time for example in July 1988 where 116mm fell in 1 ½ Hrs. Extended heavy rain such as in February 1990 and 1992 completely overtax the creeks capacity and flooding of houses and property occurs. There have been earlier flood occurrences in this area in 1975 and 1984/5.
1988	29 April 30 April 5 July 6          July	77 78 76 116
1990	3 February 4 February 7 February      19        March	270 140 165+ 79
1991	10 June 11 June	146 107
1992	9      January 9         February 10       February	116 175 133
1998	18       May 19       May 6         August 7         August  8         August	68 68 88 79 62
1999	25  February 26  February 2          April	107 32 59
2002	4         February 5 February 6 February	52 87 72
2003	12 March 14       March 15       March	134 84 57

The above figures have been provided courtesy of  Les Walker who lives in near proximity to Mudflat Creek. Les is a wealth of knowledge on the Mudflat creek flood occurrences. Les and other residents of the area are now very disappointed that the sedimentation of their once deep tidal creek has been allowed to happen and that Gosford Council of late seems to have turned a blind eye to their plight.

HB 42

February 1999, flooding of Mudflat Creek extends right through number 59 to Fraser Road.

HB 43

February 1999, Mudflat Creek in full flood, covers rear of 59 Fraser Road.

HB 44

Rock walling of upper Mudflat Creeks banks stops prematurely behind 46 Fraser Road.

HB 45

Damage done to the creek banks at the rear of 45 Fraser Road 1990.  Washed away banks end up in the Bay.

HB 46

Residents try to stabalise creek banks at the rear of 45 Fraser Road.

HB 47

February 2002, Mudflat Creek cannot handle 3 days of heavy rain without breaking it’s banks and flooding adjacent properties.

HB 48

February 2002 floodwaters invade property lower Mudflat Creek area.

HB 49

HB 50

July 1988.  Silt buildup under the Noble Street bridge prevents all of the water from flowing along the creek.  It is forced to flow around the bridge,  across Noble Street and into the mangroves.

HB 51

July 1988.  Creek floodwaters backup not far upstream from the Noble Street bridge.

Conclusion

Hardys Bay is an environmental disaster and fast disappearing as a bay, so

we have two basic choices :-

 (1) We can start now to plan, and then implement the environmental rehabilitation of Hardys bay to better than its former glory or,

(2) Do nothing and let the relentless silt build up and resultant mangrove proliferation fill in the bay and turn it into an  inaccessible swamp and, in so doing exacerbate the already serious flooding problems in the Killcare extension area.

The residents of the Killcare Peninsula want a navigable bay                    

not a mangrove swamp !!!  

Acknowledgements

Local residents to be thanked for their valued assistance with the authors photo and fact finding are as follows:-

Les Walker, Les Sauter, Keith Dunn, Bert and Jean Myer, Bruce, Irene and Ruth Dunlop, Les Sparks, Bill and June Murphy, Dorothy Jenkins, Joyce Dalzell, Gwen Perrie, Fay Gunther, Robin Warburton, Kel Gulliver and Bill Leddy.

Thanks also to Jeff  Potter from the Gosford Library and Michelle Biddulp, Louese Gee, Monkieth Kadum, Victor Tysoe and Gary Poll from Gosford Council.

For an understanding of the structure and involvement of other relevant government organisations in the future rehabilitation of Hardys Bay thanks goes to :-

Algis Sultas and Neil Kellerher from the Department of Infrastructure, Planning and Natural resources, Brian Hill and Rob Williams from Fisheries and Darren Watson from Waterways.

Thanks also to Steve Bell who assisted the author with the compilation of this report.

Footnote

Readers are advised that this study is ongoing, and the author welcomes input in the form of facts and photographs that may enhance the content of this initial publication. As additional information comes to hand further revisions of this study will be compiled by the author and made available to interested parties.