Albany Waterways Resource Book: Catchment clearing

Albany Waterways Resource Book:
Managing waterways

Catchment clearing

The catchment of the Albany harbours has been extensively cleared of vegetation for agriculture. The average percentage of cleared land within the subcatchments of Princess Royal Harbour and Oyster Harbour is about 35% and 72% respectively.

Investigations into the coastal catchments of estuarine systems of south-western Western Australia have shown that there is a strong link between the percentage of catchment cleared and the nutrient loss from a particular catchment. Nutrient loss increases exponentially with an increase in the percentage of catchment cleared.

Table 9-4: Percentage of cleared land in subcatchments in the Albany harbours catchment

Catchment Subcatchment Total area (ha) Area of private bush (ha) Area of reserves (ha) Area of cleared private land (ha) % of private land cleared % of catchment cleared *Drainage density (m/ha)
Princess
Royal
Harbour Robinson Drain 689 29 36 625 96 91 5.5
CSBP 675 25 75 575 96 85 ?
Albany town 472 72 169 231 76 49 ?
PRH 6515 1796 3198 1521 46 23 18

8351 1922 3478 2952 61 35 14.5

Oyster
Harbour King 16805 308 280 16217 98 97 8.1
Mill Brook 16224 921 1591 13713 94 85 7.3
Upper Kalgan 202719 16156 52723 133840 89 66 8.2
Lower Kalgan 41852 3777 1166 36909 91 88 6.2
North Oyster 8683 1820 777 6087 77 70 8.9
Chelgiup 5055 759 ? 4297 85 85 4.8
Willyung 3404 103 254 3047 97 90 10.7
Johnston Creek 6193 1282 1722 3189 71 51 4.2
Yakamia 2133 78 301 1778 96 82 7.8
Albany town 1024 ? ? ? ? ? ?

304092 25204 58814 219077 90 72 7.7

Catchment	Subcatchment	Total area (ha)	Area of private bush (ha)	Area of reserves (ha)	Area of cleared private land (ha)	% of private land cleared	% of catchment cleared	*Drainage density (m/ha)
Princess Royal Harbour	Robinson Drain	689	29	36	625	96	91	5.5
CSBP	675	25	75	575	96	85	?
Albany town	472	72	169	231	76	49	?
PRH	6515	1796	3198	1521	46	23	18
	8351	1922	3478	2952	61	35	14.5

Oyster Harbour	King	16805	308	280	16217	98	97	8.1
Mill Brook	16224	921	1591	13713	94 85	7.3
Upper Kalgan	202719	16156	52723	133840	89	66	8.2
Lower Kalgan	41852	3777	1166	36909	91	88	6.2
North Oyster	8683	1820	777	6087	77	70	8.9
Chelgiup	5055	759	?	4297	85	85	4.8
Willyung	3404	103	254	3047	97	90	10.7
Johnston Creek	6193	1282	1722	3189	71	51	4.2
Yakamia	2133	78	301	1778	96	82	7.8
Albany town	1024	?	?	?	?	?	?
	304092	25204	58814	219077	90	72	7.7

* includes twice the length of road as an estimate of road drains, but does not include farm and paddock drains
? unknown
(source: South Coast Estuaries Project Group 1991)

Figure 9-5: Percentage of catchment cleared vs. phosphorus export in the South-West near coastal estuary catchments
(Source: Bott, G. M. 1991, cited in South Coast Estuaries Project Group,1991)

Protection and enhancement of fringing vegetation

The health of a waterway is very much influenced by the health of its fringing vegetation.

This is a problem for the Albany harbours. To stop more nutrients gettings into the harbours, clearing needs to stop in the catchments and more work needs to be done to restore vegetation.

Currently, AgWA assesses land clearing applications under the Soil and Land Conservation Act. Under the Act landowners who want to clear one hectare or more must give AgWA a `Notice of Intention to Clear'. AgWA's assessment of these applications is carried out according to guidelines for clearing on the South Coast. The guidelines only prevent clearing when it would result in land degradation or eutrophication of waterways. This rule has been set under the Soil and Land Conservation Act.

To reduce the chance of nutrient-rich run off entering a waterbody, the guidelines recommend that a buffer strip of natural vegetation should be left along each side of inlets, rivers and creeks. The guidelines also suggest not clearing areas that are susceptible to land degradation problems such as wind and water erosion, high salinity and water logging.

Table 9-5: Guidelines for buffer zones

Waterbody Buffer Zone
Inlets 75 m buffer to be left from the natural vegetation line
Rivers 50 m buffer to be left from the natural vegetation line (rivers are defined as all permanent watercourses marked on 1:50000 map)
Creeks 25 m buffer to be left from the natural vegetation line, (creeks are defined as all permanent water courses too small to be marked on 1:50000 map)

Waterbody	Buffer Zone
Inlets	75 m buffer to be left from the natural vegetation line
Rivers	50 m buffer to be left from the natural vegetation line (rivers are defined as all permanent watercourses marked on 1:50000 map)
Creeks	25 m buffer to be left from the natural vegetation line, (creeks are defined as all permanent water courses too small to be marked on 1:50000 map)

Since 1990 the Oyster Harbour Catchment Group, AWMA and AgWA have researched the condition of the major waterways and their fringing vegetation. Original studies by Dr Luke Penn surveyed the Kalgan River in 1992-93. In 1997 a survey of the King River and major tributaries of the Kalgan River were done. The surveys findings are available to land owners and landcare groups. The information is used to work out priorities for helping with fencing along the waterway, weed control and other rehabilitation work.

The protection of fringing vegetation by getting rid of weeds and putting up fencing to keep stock out of foreshore areas is vital to keep banks stable, prevent erosion and reduce nutrient input to the rivers and harbours.

Contents:Key environmental problems of Albany's waterways