Cost–benefit analysis for riverbank erosion control approaches in the steppe area

Riverbank erosion is an important topic in environmental research. Although several methods have been used to prevent erosion and balance ecosystems, both are still very challenging issues. We propose three different adaptation approaches to control riverbank erosion in the steppe area. The area has been affected by dramatic erosion over the past several years due to water flow and other external effects. The approaches were based on bioengineering and mechanical methods that were different in terms of the erosion rate and slope of the riverbank, the velocity and intensity of water flow, and the mechanical properties of the soil and plant species. Cost–benefit analysis (CBA) and sensitivity analysis were applied to estimate and compare the approaches. The most appropriate approaches were selected by comparing the net present value (NPV), the benefit–cost ratio, and the internal rate of return, which are the main indicators of CBA. The CBA results indicated that all the approaches had positive benefits in 2020–2030. The most economically and environmentally beneficial approach was Approach-3 (bioengineering method). A Monte Carlo sensitivity analysis demonstrated that the NPV of Approach-3 was positive in both scenarios of the pessimistic and optimistic cases of the discount rate. Monte Carlo analysis with 500 simulations was performed to obtain the future NPV. The results reveal that bioengineering methods for riverbank erosion control have higher environmental benefits and are more suitable in steppe areas.