Abstract Assessing cumulative effects are a vital task for strategic environmental assessments (SEA) but lack of consistent methodology has hampered the development and implementation of useful tools. We present a model for GIS and multivariate analysis to assess the effects on a valued ecosystem type at a regional scale based on the sum of impacts of local projects. We demonstrate application of the model by assessing how hydropower developments would generate cumulative impacts on river gorges for a county in northern Norway. We use principal component analyses (PCA) of spatially-explicit variables from the region to describe the diversity of river gorge ecology with a mathematical low-dimensional bioclimatic space. We then calculate cumulative effects of hydropower development as the proportions of subspaces of the multidimensional bioclimatic PCA that are affected by either existing infrastructure or planned and possible hydropower developments. The results showed that adding development of all potential sites for small-scale hydropower would have substantial impacts on over half of all bioclimatic segments where gorges were registered and more than 70% of all segments with forested river gorges. By demonstrating these possible cumulative effects we can illustrate the need for caution in hydropower planning to avoid reducing river gorge representativeness and diversity. The method can be applied for other types of development projects and other valued ecosystems, provided the assessed ecosystems and development installations can be mapped or modelled over a sufficiently large area.

中文翻译：

---

使用 GIS 建模和代表性评估评估小规模水电开发的累积效应

摘要 评估累积影响是战略环境评估 (SEA) 的一项重要任务，但缺乏一致的方法阻碍了有用工具的开发和实施。我们提出了一个 GIS 和多变量分析模型，以根据当地项目的影响总和来评估对区域范围内有价值的生态系统类型的影响。我们通过评估水电开发如何对挪威北部一个县的河流峡谷产生累积影响来展示该模型的应用。我们使用该地区空间显性变量的主成分分析 (PCA) 来描述具有数学低维生物气候空间的河流峡谷生态的多样性。然后，我们将水电开发的累积效应计算为受现有基础设施或计划和可能的水电开发影响的多维生物气候 PCA 子空间的比例。结果表明，增加所有潜在小规模水电站点的开发将对超过一半的有峡谷登记的生物气候段和超过 70% 的有森林河流峡谷的段产生重大影响。通过展示这些可能的累积效应，我们可以说明在水电规划中需要谨慎以避免降低河流峡谷的代表性和多样性。该方法可应用于其他类型的开发项目和其他有价值的生态系统，