ACARP Geomorphic Criteria

Mining impacts on both the quality and quantity of water are a highly contentious aspect of most mining projects [22,94]. The performance of river relocation channels was studied by a series of ACARP initiatives within the Bowen Basin, Queensland (Figure 8). The result of these investigations was the establishment of specific hydraulic and geomorphic design criteria for these regional watercourses.

Hardie and Lucas [86] assessed 35 natural reaches of streams that had not been altered within the region and identified significant relationships between the hydraulic parameters in three variable stream types (incised, limited capacity, and bedrock controlled). These distinct stream parameters could then be used in the design of new relocated channels, and the rehabilitation of existing channels that were poorly performing or degraded [86]. These hydraulic parameters act as guidelines and establish the ideal range of conditions within each stream type within the region (Table 3).


**Table 3.** Characteristic values for stream sample reaches [86].

The hydraulic parameters in the guideline were refined in an additional study that evaluated the performance of 60 relocated channels, where 17 had been constructed following the guidelines. The 17 artificial channels constructed using the guidelines were found to be in better overall condition than the rest of the relocated channels [48]. An outcome of these ACARP projects was the production of a series of updated stream parameter guidelines (Table 4) that provide a design approach for relocated alluvial and bedrock channels. Additional elements were also considered, including the level of sediment supply to the relocation channel, and channel and planform variability [70,72]. This integrated design increased the likelihood of successful vegetation establishment.

**Table 4.** Revised criteria for river relocation designs [70,72].


In 2014, the Government of Queensland consolidated the earlier principles of design for river relocated channels, based on the ACARP recommendations, to produce a series of design objectives (Table 5). These objectives indicate that relocated channels should be self-sustaining, include geomorphic and vegetation features similar to the regional watercourses, positively contribute to river health values, and impose no long-term liability on the state, the proponent, or the community [16].

**Table 5.** Government of Queensland Key Principles of design for river relocation channels [16].

1. Permanent watercourse diversion incorporates natural features (including geomorphic and vegetation) present in landscapes and in local watercourses

2. The permanent watercourse diversion maintains the existing hydrologic characteristics of surface water and groundwater systems

3. The hydraulic characteristics of the permanent watercourse diversion are comparable with other local watercourses and suitable for the region in which the watercourse diversion is located.

4. The permanent watercourse diversion maintains sediment transport and water quality regimes that allow the watercourse diversion to be self-sustaining, while minimizing any impacts on upstream and downstream reaches

5. The permanent watercourse diversion and associated structures maintain equilibrium and functionality and are appropriate for all substrate conditions they encounter.
