At our October 2015 workshop, Will Alison, a great young farmer from the Central West of NSW, was wandering around our farm and specifically up and down our creek, and he came to us and said that this coming workshop, he would like to show people various ways of restoring a damaged creek. Our creek, Dry Creek, is a typical example of a damaged creek.
As a small child growing up in the city, even an Australian city, when someone spoke about a creek, I had images of the babbling brook type of creek, water bubbling over rocks, cool and refreshing, maybe the occasional fish or frog, just like my picture books. And I've even seen such creeks in Australia, but not often in our part of Australia. We live in a brittle environment. A brittle environment is one where the humidity just above the soil surface is very low and this has all sorts of ramifications for how we should farm - and how we should bring our creeks back to health.
What are the signs of an unhealthy stretch of creek?
- creek bed is dry most of the time (I did say our creek was called Dry Creek, didn't I?!). The corollary of that is low water tables
- deep incised channels - the creek is no longer in touch with its flood plain, i.e. when the waters do come (and come they eventually do), the creek bed is so low that floods occur only within the channel and don't spill over onto the flood plain, thus fertility and water are lost from the local system
- head cuts in the creek bed - these are where there is a distinct drop from one level to a lower one in the creek bed. At the next significant rain event, the waterfall created could undercut the higher level of the creek bed and thus drop the creek bed to the lower level for hundreds of metre upstream. This is the fastest way to create deep incised channels
- significant erosion on the creek banks with steep un-vegetated slopes
What are the signs of a healthy stretch of creek?
- creek bed holds water most of the time. Even if the creek is not flowing, there should be deep water holes in the creek bed
- The creek is only a small shallow channel with banks that are raised a bit above the flood plain. The banks are created from the deposition of silt when the creek spills over into the flood plain during a significant rainfall event.
- any waterfalls in the creek are protected by rocks so the creek bed is more stable
- creek banks are stabilised by vegetation
How can we restore a creek to health?
The most important thing to focus on is to slow the water down. Water in itself doesn't cause a lot of damage. Water at high speed is what causes damage.
- increase infiltration of water into the soil - anything you do to increase water infiltrating into the soil and reduce it sheeting off across the surface will slow the water passing through the whole farm system and increase the water in the system where it is needed most, i.e. the soil and the aquifers. It includes such things as cell grazing (as per Allen Savory's Holistic Management techniques) and deep ripping the hills on contour and or keyline with a Yeoman's plough (as per "Water for Every Farm - Yeoman's Keyline Plan")
- gentle the water as it moves down the creek - here you can build structures such as Zuni bowls and one rock dams, log and fabric step falls, filter dams. These have been used in New Mexico to heal a lot of ailing river systems. And these are the sorts of things that Will is interested in building in our creek.