[Pil-pc-oceania] Compacting / protecting stream banks

[Robyn Williamson]

Hi Linda

I am not an indigenous "psycho" and have never even heard of  
Gisborne, however I do believe in choosing native over exotic species  
wherever possible.

Try to get the native Pennisetum alopecuroides instead of Pennisetum  
setaceum out of Africa or you might be sorry later when P. setaceum  
runs amok all over your property.  The seeds are normally spread by  
wind but water is also a good carrier of bulk quantities of weed seed.

Alnus or Alder is a good, reasonably fast-growing, deciduous (free  
mulch from heaven) specimen for deep soils in cool moist locations  
where winds are not to severe.  The cut timber is particularly  
durable in wet soils.  But watch out for self-seeding because the  
seed germinates readily in autumn when ripe and again they are spread  
by the wind.  Choose from Alnus jorullensis or Mexican Alder (from  
Mexico and parts of Central America) which may reach a height of  
12-15m in good conditions, Alnus glutinosa or Black/Sticky Alder  
(from Europe, North Africa, Turkey and Siberia) 20m, Alnus cordata or  
Italian Alder (from southern Italy) 12-20m, Alnus incana Grey/ 
Speckled Alder (from Europe to western Asia, USA & Canada) 15-20m.   
Cultivars such as "Aurea" (sounds like it would turn golden in autumn  
but actually a dull yellowish colour), "Laciniata" (with leaves cut  
half-way to the midrib), "Imperialis" (more deeply cut leaves giving  
them a lacy appearance) and "Pyramidalis" which has an erect, narrow,  
compact but still conical shape with ascending branches, as opposed  
to the semi-pendulous or drooping branches of other varieties.

Any big landscraping mob should have or be able to get the machinery  
you require, you'll have to get their advice about the angles they  
can work at but my understanding is that erosion is erosion and it  
can only be "fixed" by planting.  If you have the banks compacted it  
will be harder to germinate seed or establish small seedlings along  
the banks.

You are right ... if the plants aren't well established before the  
spring rains they won't make much difference, in fact many of them  
could be washed away downstream especially if the flow is fast and  
constant. Biodegradable geotextiles that hold the plants on the banks  
in place while they establish are readily available from  
landscrapers, I would suggest that you check out this option too.

Best regards,
Robyn


CONTACT DETAILS:

Robyn Williamson
APC9 Secretariat
info at apc9.org.au
Ph/Fx:  (02) 9629 3560
Mobile:  0409 151 435
http://apc9.org.au



On 22/02/2008, at 1:40 PM, stevehart at maxnet.co.nz wrote:

> my memory of Gisborne
> including the name it has many exotic species prevalent...so you  
> may have
> no concerns over using exotic material...IMO you'll need to get some
> aggressive large specimen grasses into the bank ready for any autumn
> rains.....of course there are many Aust native grasses that do really
> well...many are used in city landscapes...mass plant them...you  
> could also
> consider the pennisetum varieties..large aggressive  
> varieties...there are
> some Aust natives in nthis family . The larger Poa varieties will  
> do well
> also. But be aware that you will need to plant shrub and tree cover  
> too
> for the grassess will support water running off rather than being  
> absorbed
> as the shrub and tree roots will. If ya not an indigenous psycho a  
> good
> river/straem bank tree is Alder or Alnus ...

>> Date: Fri, 22 Feb 2008 12:43:11 +1100
>> From: Linda Shewan <linda.shewan at bryn.com.au>
>> Subject: [Pil-pc-oceania] stabilising / compacting stream banks
>> To: permacultue discussion list
>> 	<pil-pc-oceania at lists.permacultureinternational.org>
>>
>> School management had a stream/diversion drain put in to divert  
>> water from
>> our school carpark down to the dam and wetlands at the back of the  
>> school.
>> This was completed in November. The good news is that the dam is  
>> full! The
>> bad news is that the stream banks were not compacted and there is  
>> a lot of
>> erosion happening as water runs off from all over the school.
>>
>> I understand you need a sheet foot roller or a vibrating sheet  
>> foot roller
>> to compact dams etc properly.
>>
>> Does anyone know of anyone around Gisborne, VIC  that has this  
>> equipment?
>>
>> And does anyone know what angles they can work at? The creek sides  
>> are
>> angled about 45 degrees.
>>
>> Any other ideas... we are looking at funding for planting to  
>> stabilise the
>> banks but winter will be upon us by then and they will not be  
>> established
>> enough to make any real difference for this year I would think? Or  
>> am I
>> wrong in that assumption?
>>
>> Thanks for your help, Linda
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