River training works Problems and solutions ANY REPRODUCTION, INCLUDING PHOTOCOPY, FILM AND MICROFILM, IS FORBIDDEN. ALL RIGHTS RESERVED WORLDWIDE. FILM AND MICROFILM, IS FORBIDDEN. ALL RIGHTS RESERVED ANY REPRODUCTION, INCLUDING PHOTOCOPY, Quality System Guarantees Production, certified internal management and technical assistance in compliance with ISO 9002. Environmental Officine Maccaferri S.p.A. solutions Via Agresti, 6 - P.O. Box 396 40123 Bologna - Italia Tel. ++39 051 6436000 Fax ++39 051 236507 e-mail: [email protected] Website: www.maccaferri.com © 2000 Officine Maccaferri S.p.A. - Bologna - Italy - Print: Tipografia Labanti e Nanni - Project: Grafica Monti - Photo: Archivio Officine Maccaferri Environmental solutions Maccaferri solutions for river training works and erosion control - Channel linings - Bank protections - Weirs - Groynes Most of the towns and cities we know today have deve- communication routes were required for trade and social loped in areas that have been inhabited from ancient exchange. It is difficult today to ignore the problems of times. Meanders or islands in rivers have always been flooding of low lying areas and the need to protect roads, favourite sites for human habitations in order to take railways or industrial buildings. advantage of the availability of water and fertile land for However, we must not forget that a natural watercourse farming. Thus began a relationship between man and the is a living entity in continual development that should river which has been developing ever since. With the be protected, as far as possible. increase in population and the development of industry, Italy 03 For a well-balanced design of river works By analysing the main factors which are important in the maintenance of a well-balanced river habitat when looking at its restoration one 1 2 4 3 not only has to choose which materials are to be used but also to make a proper evaluation of design methodologies. A natural river course is characterised both 1. Habitat 1 = roots of Salix sp. covered with tufts from plan and elevation and dictated by the Cladophora Sp.; 2. Habitat 2 = silt deposited on gabion protection; need to maintain environmental bio-diversity. 3. Habitat 3 = neuston around the groynes; Design hypothesis and technical solutions can 4. Habitat 4 = stagnation point. be a common denominator and bioengineering should not be considered as a list of techniques U.K. (foto David Barker - Edenbridge U.K.) Microhabitat check schematisation but as a global approach philosophy. (Research on the environmental effects by rivers sides with Gabion and Reno mattresses)-Italy 1993-1994. This means that solutions must relate to the Italy - Actual situation problems, avoiding both technical and ethical mistakes, and without excess, all within a multidisciplinary approach where engineers, biologists, botanists and architects do not prevaricate each other. The solution must: - supply the immediate required stabilisation; - promote a positive evolution (re-naturalisation) of the new ecosystem created from the river training works. Belgium PROBLEM POSSIBLE SOLUTIONS HYDROSEEDING LIGHT REVETMENT REVETMENT WITH GRAVITY WALL WITH REINFORCED SOIL WITH GEOMAT RENO MATTRESSES GABIONS STRUCTURE APPROVED SOLUTIONS CORRECT SOLUTION PROPOSED SOLUTION CORRECT SOLUTION PROPOSED SOLUTION OVER DESIGNED UNDER DESIGNED Belgium - Actual situation 04 05 The solution exposed in the previous pages have to be A system of softwares chosen on the basis of quantitative analysis and not only for hydraulic and qualitative or subjective ones. This is the reason why our company has promoted labora- environmental design tory, field and bibliographical researches, on the basis of which a series of specific software have been created MACRA 2 The MACRA2 / Weirs software was MACRA developed to conduct hydraulic (By EHS Bologna - Italy) and static analysis of gabion The MACRA software, working in an Autocad weirs. format, allows the engineer to design the river training works in a stretch of river under the hypothesis of a steady flow, taking into account the actual river geometry, rou- ghness and flow normally present in a natu- ral watercourse. MAQUA MAQUA is a software developed in a Win- dows format, supporting the design of river training works, Environmental Impact As- MACRA 1 sessments (EIA) and allowing for the ma- The MACRA1/Bank Protection software, whi- nagement of watercourses. MAQUA's pur- ch uses a Windows type structure, provides pose is to provide a model for the engineers with a rapid and efficient tool with evaluation of the environmental value of which to conduct the stability analysis of watercourses subjected to intervention. watercourses cross-sections with respect to This program compares design alternatives both water flow and wave motion. and selects the one shown to preserve the initial environmental value. 06 07 Longitudinal Revetments structures When an erosion process that does not affect the global stability creates slope The term longitudinal structures is used to de- instability, then revetments can be a fine structures with their length parallel to the possible solution. river flow. These structures are often built on The choice of the most suitable type of existing natural banks and they usually revetment must be made on the basis extend for a considerable distance. of a comparison between the acting Italy They are used for a variety of purposes, stresses (in terms of shear stresses and such as: not only water velocities) and the ser- - erosion control viceability limits of the material used. Italy - control of meanderings The approach to be considered must - containment of the normal flow channel always be made under the term of Bio- - flood protection engineering, based on a combination of live and inert materials where the limitations of both must be taken into consideration. Italy Italy Italy Italy Italy - Actual situation Italy - Actual situation 08 09 Gabion gravity structures A bank stabilisation may involve the construction of a retaining structure that should not only effect the natural filtration between the watercourse and Italy the bank, but must also guarantee the required consolidation. Furthermore, the presence of subgrades and banks that are normally saturated or which have unpredictable erosion phenomena make the application of flexible structures a necessity. They must Italy Italy be able to withstand differential settlement without loosing their structural integrity. Maccaferri gabions are fabricated from high The utilisation of double twisted hexagonal mesh Gabion structures are the ideal solution quality steel wire where long term durability is also guarantees high flexibility and resistance, on account of their flexibility, natural guaranteed by galvanising with either zinc or a all adding to the main characteristics that make drainage capacity due to the stone filling, zinc/aluminium alloy, that can be further Maccaferri gabions the ideal solution and high structural resistance. protected by a polymer coating and all of which for river bank stabilization. comply with the highest international standards. Italy Italy Italy Italy 10 11 Gabion gravity structures Greece The wall must be founded at a level that is not affected by water scour problems. Generally a direct foundation of this type is only advisable where the river bed material is un-erodible or when it consists of solid rock. It is also appropriate in mountainous regions and especially in the wilder torrents where the heavy bed load could damage Italy elements such as aprons protruding into the stream bed. It is not always possible to build the foundations of river bank improvements in the dry. Italy In these cases a platform In A gabion apron extends horizontally in to these cases a platform can be the bed so that it adjusts to possible built of dumped rock or scouring thereby providing an adequate cylindrical gabions, and the foundation for the protective structures built vertical portion of the protective upon it. structure can be conveniently built A properly sized apron should extend on top. horizontally into the river bed beyond the If the platform is built of loose rocks vertical front face of the protection by 1.5 it is particularly important to choose to 2 times the maximum depth of expected a rock size to ensure the stability of scour. This ensures that under maximum the super-structure. scour conditions, the apron will fold down into the scour hole without being too steep or allowing the surface to take up a “quilted” or undulating profile. U.K. Brazil 12 13 Reinforced soil structures Italy The development of new technologies such as The Terramesh® System are structures whose component reinforced soil structures using the combined strength sizes are pre-determined and completely pre-assembled of the soil and the reinforcing elements has opened during the production phase. Each element has two up new methods for the stabilisation of riverbanks. main properties: the first to reinforce soils, and the The double twisted wire mesh Terramesh® System second to stabilise the face. The ordinary Terramesh® (made with polymer coated Galmac® wire) has greatly has an external face similar to stone filled gabions. extended Maccaferri’s experience in the field of The Green Terramesh® has a face lined with a geomat revetments and gabions. that retains uncompacted vegetable soil. Terramesh Verde Terramesh System Italy Italy - Actual situation Italy 14 15 Gabion weirs Gabion weirs are classified in three types, according to the shape of their downstream face at the centre of flow: - vertical weirs - stepped weirs Italy - sloped weirs Brazil The vertical weir is certainly the simplest type, and is often used for small weirs in a system controlling a reach of a stream. Since this means that the gabion mesh is protected against abrasion and impact by heavy bed material carried in spate conditions, it is a type recommended for training works on mountain torrents. Italy In the design of vertical weirs, maximum attention must be paid to the dissipation of the kinetic energy of the cascade which is allowed to scour the bed thus forming a pool.