What monitoring and maintenance schedules and maintenance costs could be embedded in small-scale gully remediation plans?
Monitoring and maintenance schedules
The results of this study suggest that most sites would benefit from two to five years of monitoring and maintenance, with longer times frames for difficult sites. A site-specific risk assessment done at the planning stage will help determine an appropriate time frame.
The monitoring of land condition at catchment sites should take place every year, preferably at the same time( e. g. end of dry season). These can be included in the annual round of land condition assessments carried out on the property. Structures installed in catchments and in gullies should be monitored during and / or at the end of each wet season. In this way, any maintenance required can be planned for the dry season, perhaps coinciding with other earth works such as track maintenance.
Maintenance costs on catchment works
Maintenance schedules and budgets should be low for catchment works although any earthen structure such as diversion banks will require maintenance in time to maintain its integrity. One of the five catchment only sites required maintenance, and this was around 80 per cent of the initial costs. The repairs were required because the initial construction did not follow basic soil conservation guidelines.
Maintenance costs on gully works
Half( 7 / 14) of the remediated small-scale gullies required maintenance and this had a large negative impact on the cost-effectiveness of the site( Table 4). For five of the seven sites maintenance costs were between 30 per cent and 80 per cent of the initial costs. When total maintenance costs are shared across all the remediated small-scale gullies the average maintenance costs was $ 8,600, which is around a third of the average initial cost. Even though mobilisation costs constitute a large proportion of this expense, maintenance costs should be lower. The main reason for this is that most of these maintenance jobs were at sites where initial works did not follow best practice. It is anticipated that if expert advice is followed and the recommendations such as those derived from this project are considered, maintenance requirements for similar sites under average environmental conditions would be fewer and less costly.
Timely maintenance, especially during the first wet season following initial works, was essential for the success of two of the small-scale gullies, as well as for four of the large-scale gullies. The two small gullies are in a favourable condition( mostly stable) because of the landholders’ commitment to their project. They mobilised machines, sourced rock and made repairs as soon as the first rains started to cause damage, despite it being Christmas.
Landholders who do not have earthworks machinery readily available, or are unlikely to organise repairs should be discouraged from undertaking remediation that involves heavy earthworks, such as rock chutes and diversion banks. Low risk alternatives such as gully head fills, shallow ripping or stick lines are likely to be more appropriate in the long term.
Lesson learnt: It is important to do a good job during the initial work to avoid high maintenance costs. Sometimes repairs will need to be done promptly, while at other sites such as in the catchment, maintenance can be done strategically to share mobilisation costs.
52 GULLY MAINTENANCE AND MONITORING TECHNICAL REPORT