Benefits, co-benefits, and trade-offs in natural water retention measures: a review of classifications and indicators

In recent years, natural hazards related to climate change, such as extreme floods, droughts and heatwaves, have increased in magnitude and frequency. In response, Natural Water Retention Measure (NWRM), as a vital strategy to mitigate these challenges, focuses on increasing and/or restoring the retention capacity of soil and aquatic ecosystems. NWRMs can have positive impacts that may lead to several benefits and co-benefits. They can also have some negative impacts, in the form of trade-offs. To assess the efficacy of NWRMs, it is essential to consider and evaluate both multiple benefits and trade-offs in a comprehensive framework and use appropriate indicators for their assessment. Through a literature review, it is found that there is no thorough study that examines the different types of benefits and co-benefits, provides a complete classification of the benefits and co-benefits of NWRMs, and introduces various indicators for their evaluation. In addition, trade-offs associated with NWRM are sometimes mentioned in the existing literature, but the different types of trade-offs are not fully listed. In this regard, and for the first time, the present study aims to provide a classification of both the positive and the negative impacts of NWRMs and a list of different indicators related to various types of benefits and/or co-benefits. The study also shows major challenges in assessing NWRMs efficacy, including the spatial and temporal scale of the data and indicators, combining qualitative indicators with quantitative indicators, trade-off quantification considering social, economic and cultural aspects, and human perception.