In the Urdaibai Biosphere Reserve, BC3 in collaboration with NEIKER developed a model to assess how different forest management strategies affect soil erosion and sediment deposition in the Mape and Artzuola sub-basin. We analysed three possible scenarios:
- Business As Usual: assumes current forest management practices will continue
- Riparian Buffer: implements a 25-meter buffer zone around the river where a riparian forest is established
- URBASO: creates three protection zones around water abstraction points, in addition to the riparian buffer zone (see B2.1, B2.2, B2.3 and B2.4 actions for further information on protection zones).
To simulate soil erosion and deposition, we used the USPED (Unit Stream Power-Based Erosion Deposition) model, which builds upon the widely used RUSLE (Revised Universal Soil Loss Equation) model by also considering where sediments are deposited, not just where erosion occurs. The model takes into account key factors such as:
- R factor: rainfall-runoff erosivity index
- K factor: soil erodability index
- LS factor: slope length and steepness
- CP factor: soil cover and management practices
The results were clear: implementing protective buffer zones upslope of water abstraction points intended for human consumption significantly reduces soil erosion and sediment accumulation, with the URBASO and Riparian buffer scenarios proving to be more effective in protecting water quality and soil rather than Bussiness as Usual scenario.
These findings suggest that establishing buffer zones around rivers and water abstraction points could improve water quality and help protect soil. However, their effectiveness depends on the specific characteristics of the watershed, so we recommend combining them with hydrological analyses to determine the best locations for implementation.
See also: URBASO B4 ARIES Deliverable