Incorporating the erosion sensitivity of local soils in a levee safety analysis

This report aims to provide the POV DGG with an inventory of the available established international knowledge with respect to erosive properties and erosion resistance. Feedback obtained from endusers during webinars organized by the POV DGG, has been adopted in this second version of the report. In terms of content, the report covers only one aspect of how soil properties affect levee design, and what instruments are available to account for erosion in levee safety analyses. Other reports developed as part of the POV DGG deal with the impact of other failure mechanisms. The report finishes with recommendations on how the current knowledge could be extended to facilitate the design of levees with local soil. This report thereby focuses on qualitative descriptions of the different approaches and thereby only mentions quantitative prediction methods in case this also serves an indicative purpose. The research into the field of erosion has led to numerous predictive formulae. The author aimed to evaluate only those approaches for which reasonable consensus exists. Despite this consensus the author attempted to remain critical of the approaches. Equations and erosion parameters, that are mentioned in this report, have been peer reviewed and/or have been adopted in several commercially available models. References are provided with the information such that readers may provide themselves with more details. The report also comments on how the available methods fit within the “Story of the Levee” concept, which is one of the 5 objectives of the (Evaluation and design instrument) BOI and in underlying the Knowledge development programme (KvK) of Rijkswaterstaat WVL. The report has been written with the aim of the POV DGG in mind and aims to provide a technical framework for evaluating erosive properties of soil.

Chapter 2 of this report discusses the framework within which erosion relations have been applied internationally. Chapter 3 discusses which proven methodologies are available to determine the erosive properties of soils, how these depend on soil properties, and what weaknesses and strength the methods have. Chapter 4 subsequently discusses a method of categorizing the different measurements of soil erodibility and provides an overview of the current level of knowledge (inter)nationally. Chapter 5 contains a discussion on how to utilize small-scale tests to facilitate the used of local soil in levee designs. The discussion leads to the recommendations made in Chapter 6. The author acknowledges that the use of erosion models for safety assessment of levees is still in its infancy. The aim is therefore not to focus on what gaps in knowledge are occurring, although these certainly are addressed, but is to focus on how the available methods can be used.