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Re-Imagining Landscapes #1: Drainage Systems

January 20, 2018

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Re-Imagining Landscapes #1: Drainage Systems

January 20, 2018

As both an Earth Scientist and a Landscaper, I am forever exploring ways to not only improve the aesthetic appeal of a given space, but also enhance its ecological functionality. Whilst working at The Riversdale Golf Club in Mount Waverley, I had ample opportunity to marry my designer-eye with my academic background in earth science and ecology. By coalescing these two disciplines, I was able to achieve a result that is both visually attractive and ecologically beneficial. 

 

One of the projects I was responsible for at Riversdale was the conversion of a traditional (and largely ineffective) pipe and grate-drain drainage system, into an attractive naturalistic drainage line. In order to achieve this, I used an assemblage of wetland and terrestrial plants and 4m3 worth of ornamental, sustainably-sourced mud-rock.   

 

 Fig. 1:  Before: Serious erosion and resultant sedimentation of the pond due to an ineffective drain and PVC pipe. 

 

 Fig. 2:  Before: An unattractive swale-like depression. The bare ground at the rear of the Carex appressa (Tall Sedge) is indicative of the excessive erosion. 


Re-imaging the Space:

The original drain had been used to capture water from higher up in the landscape, transporting it into a large pond (pictured below). During heavy rainfall and storm events, torrents of water, mulch, soil, and other suspended particulates would converge on the drain. What debris could fit in the small drain would end up blocking it, with the excess water flowing at high velocity over the surface, ultimately eroding what loose sediment and mulch had been placed there.

 

My solution to this was to remove the drain and PVC pipe, and excavate out a deeper, slightly angled (towards the pond, obviously) channel. I would then emplace mud-rock on either side of the channel. Following this, I filled the channel with rushes (Juncus subsecundus – Fingered Rush) and sedges (Ficinia nodosa – Knobby Club-sedge). Lastly, I planted Carex appressa (Tall Sedge) on the higher ground, and inter-planted it with the locally native Chrysocephalum semipapposum (Clustered Everlasting), Wahlenbergia stricta (Austral Bluebell) and the striking, grey-leaved Rhagodia spinescens (Creeping Saltbush).

 

This re-imagined space, I envisage, will reap a quadruple dividend, through: 1) improving hydrological flow by reducing erosion and subsequent sedimentation of the pond; 2) providing bio-filtration of water entering the pond (via the planting of rushes which immobilise harmful pollutants); 3) improving habitat for local fauna (lizards, frogs, birds, waterbirds, and insects) by providing food and shelter; and 4) providing a visually appealing feature for the patrons of the golf club.

 

 Fig. 3:  Construction: Careful, and artful, placement of mud-rock was necessary to both define the drainage channel and to ensure visual attractiveness. 

 

 Fig. 4:  Construction: Rock placement continues. I moved the smaller rocks around by hand to get the look I was after - channelled, but not too rigid/formal, and yet naturalistic, but not too random or visually confusing. 
 

 Fig. 5: After:  The existing Carex appressa (Tall Sedge) were relocated into bunches of three, framing the drainage channel. Chrysocephalum semipapposum (Clustered Everlasting) , Wahlenbergia stricta (Austral Bluebell), and Rhagodia spinescens (Creeping Saltbush)  were planted amongst the Carex. They cannot be seen here as they are only tube-stock size. Running down the centre of the channel are densely planted Juncus subsecundus (Fingered Rush).  I chose Fingered Rush because it is lower-growing than most Juncus species (typically reaching 50-80cm in height), relatively drought tolerant, sediment-binding, and has bio-filtration capabilities. Ficinia nodosa (Knobby Club-sedge) was also planted, mostly in-between the rocks.  

 

 Fig. 5: Before & After. Once established, this new naturalistic drainage line will not only reduce erosion and water-pooling on the path, but provide habitat and feeding sites for local fauna. These include:  the Southern Bell Frog, Striped Marsh Frog, Australian Painted Lady Butterfly, Willie Wagtail, Blue-tongued Lizard, and others. 

The Storm Event - Proof is in Pudding?:
One of the rewarding things about working on a project from beginning to end (and then sticking around to watch it work its magic) is the warm-and-fuzzy satisfaction you get. Shortly after completing this particular drainage line re-construction, Melbourne experienced a significant storm event. Below is video footage (proof!) that the new system is not only satisfying to look at, but functional. Because multi-functionality within urban green space, as a concept, is something I am deeply passionate about, I was suitably chuffed when a colleague sent me this video of my new drainage line in action:

 

 


 

 




 

 

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