INTRODUCTION
Link to WG 128 TBP Excel Selection Tables
Such green TBPs cannot be designed in the same way as their conventional counterparts because the latter need much less design information than TBPs. Because conventional bank-protection designs only need, in principle, the magnitude of ship-induced impacts and some bank properties such as the slope inclination and friction angle, conventional designs allow greater standardization than green TBPs.
By contrast, the functionality of TBPs depends on a much greater number of influencing parameters in the local boundary conditions (BCs), such as the magnitude of water-level changes (ΔW), especially the duration of drought and flood periods, which influence the possible vegetation or the elevation difference between mean water (MW) and the highest shipping level (HSW), which in turn determines the efficiency of wave-breaking pre-embankment constructions. Other important local BCs determine the vitality of vegetation; for example, the precipitation, the slope (inclination), the width of the vegetation zone, and possible shading by buildings or large trees. Other relevant impacts – besides navigation – include frost heaving or ice drift.
Different planners’ aims are also design relevant, such as the necessary stability; for example, against the dominant navigation-related loads or the fulfilment of ecological demands such as the enhancement of water-bound and terrestrial ecosystems, the creation of ecological stepping stones, or social or legal demands such as enabling recreational activities. The design of TBPs is therefore generally much more complex compared with conventional protections and led to the decision to develop a design approach based on practical experience gained from numerous implemented measures (collected in Part 2). These experiences were analysed and extended, by so-called projections using subject-matter expert knowledge from the members of PIANC WG 128. These projections include the assessment of worst-case BCs, where the measures may still function as intended according to expert assessment, and additional functionality, where the measures will offer extra functions if adaptions were implemented.
Transferring this expertise and experience represents the main challenge and purpose of this BPA. That is, this guide seeks to make available the best practices for implementing TBPs concerning the achieved stability and sustainability, the potential ecological upgrade or other planner’s aims at the implementation site (called Analysis Case, or AC), the BCs and planner’s aims at sites where a new measure is planned (called Design Case, or DC) by gathering, organizing, and presenting all relevant design criteria in a preferably quantitative way. In a PIANC report, this multicriteria approach should be facilitated as far as possible for practitioners.
LAYOUT AND CONTENT OF THE REPORT
This report, Technical-Biological Bank Protections for Inland Waterways, is split into three parts. This part, Basics of a Best Practice Approach, provides basic information about the BPA for selecting and constructing TBPs. The second part, Part 2, Library of Measures, provides detailed information on recommended TBPs that can be selected, combined, and adapted by using the BPA. The third part, Part 3, Decision-Support Advice, guides practitioners through the whole design process with a focus on selecting appropriate measures.
The report also supports planners and practitioners with numerous implementation best practices, especially in Chapter 3 of but also in Part 2, where design features of recommended measures are presented, and of course in Part 3, but the report cannot provide design guidance on every last detail (for example, concerning the necessary thickness and bonding depth of a palisade in muddy ground or the necessary extra surface weight to be placed on bank slopes in case of strong excess pore-water pressure), because these features strongly depend on local conditions.
Thus, the AHP approach (Analytic Hierarchy Process), outlined in Part 3, should be understood as an extended decision-support approach, which provides excellent information for selecting appropriate measures and enough information for concrete design in many cases, but it may need additions especially in the case of critical subsoils and strong ship-induced impacts. Reference is made concerning this point to standard design tools such as the German GBBSoft (2010).
RELATIONSHIP BETWEEN THE DIFFERENT PARTS OF THE REPORT
The three parts of the report and their different chapters are variously linked together. Generally, the link is mentioned at the end of each chapter, and practitioners can follow these links mentioned in the texts to find the right path through the report. Of course, practitioners may also read the report in sequence, but the recommended jumping from one part to another as needed supports a selective reading and applying of the report, as different parts of the report are written for different readers and practitioners. Figure 1 shows how the three parts interact with each other and which chapter practitioners and planners should read or apply. The different colours of the text and frames highlight the relationship between different parts of the report.
To further simplify the many connections between Parts 1 and 3, Chapters 1–6 in Parts 1 and 3 correspond directly to each other. They are thus shown on the same level in Figure 1. The content of each chapter is similar but not exactly the same. So, Parts 1 and 3 complement each other, whereby Part 1 focuses on the basics of the recommended design approaches for readers who either do not want or do not need details, and Part 3 focuses on the details of the approaches for readers who either want or need assistance for applying the report to a real and implemented Design Case.
CONTENT OF THE REPORT WITH ADVICE ON READING ORDER
Readers should generally read Chapter 1 of the report’s Part 1 first, using the three levels on the left in Figure 1 to guide the depth of their reading. The dotted, coloured frames on the right of Figure 1 show different readers how comprehensive each chapter is for their own application needs.
Readers interested in summaries of the report’s main objectives only (for example, decision-makers and contract makers), should read at least the abridged versions of Chapters 1 -4 in Part 3 and the corresponding summaries in Chapters 5 – 8 in Part 1. These readers might also find useful a quick review of the collection of measures in Part 2.
First-time users of the report and experts should read the corresponding comprehensive versions of the aforementioned chapters (1–4 in Part 1 and 5–7 in Part 3) and the Appendixes A–C in Part 3, which offer several worksheets for applying the BPA. During subsequent reads, practitioners may concentrate of Part 3 only, which also serves as a tutorial document.
STRUCTURE AND CONTENT OF PART 2
The comprehensive collection of measures in Part 2 is categorized into three groups, which are explained in more detail in Chapter 4 of Part 1:
- The first category contains 23 Basic Types (BTs), which provide short summaries of common measures, such as standard bioengineering methods, without specific reference to implemented measures.
- The second category contains 34 Fact Files (FFs), which provide more comprehensive and standardized information than the Basic Types, especially on the motivations of the planners, the local BCs, and the achieved functionality.
- Finally, the third category contains 6 Case Studies (CSs), which include all the information of the FFs plus additional background information and other details on the implemented measures such as their achieved functionality.
All measures, which primarily concern waterways in a temperate climate, are further subdivided into applications at sites with low, average, and high ΔW (or corresponding channel types such as canals, impounded rivers, and free-flowing rivers) and applications at sites with low up to high ship-induced impacts because analysis showed that ΔW and ship-induced impacts are generally the most important criteria for choosing the appropriate measure. This categorization allows to some extent preliminary selection of appropriate measures; see the following figures, which visualize all the measures considered in this report, including the standard example to understand the BPA – the DC at the impounded Weser close to Stolzenau town – and the AC, here willow-brush mattresses, which were implemented at the free-flowing Rhine section close to Worms, Germany.
