Renaturalization of watercourses

Ecological restoration and reclamation of aquatic environments

The renaturalization of watercourses is a fundamental step in the restoration of the ecological, hydrological and geomorphological functionalities of river systems degraded by historic developments. Faced with climate challenges and the erosion of biodiversity, these complex technical interventions aim to restore the natural dynamics of waterways while preserving essential human uses. Our expertise allows us to design and carry out renaturalization projects integrating scientific precision, technical mastery and environmental sensitivity to recreate resilient, functional and biodiverse river ecosystems in the Geneva region.

Our expertise in river renaturation

In-depth hydro-ecological diagnosis

Each project begins with a Multidimensional Systems Analysis of the watercourse:

detailed hydromorphological study (longitudinal and transverse profiles)
Precise characterization of the hydrological and hydraulic regime
Particle size analysis of sediments and erosion dynamics
Comprehensive ecological inventories (fauna, flora, habitats)
mapping of discontinuities and obstacles to ecological continuity
Hydraulic modelling of flows in different hydrological scenarios
Analysis of historical data and geomorphological evolution

This in-depth study phase allows us to establish a precise diagnosis of the dysfunctions, identify the potential for restoration and define measurable ecological objectives, thus creating a solid scientific basis for the design of the renaturalization project.

Specialized technical interventions

Morphological restoration of the bed and banks

Our interventions recreate the natural morphology of the watercourse: Remeandering : reconfiguration of the rectified route according to a calculated sinuosity adapted to the slope and characteristic flows, with prior hydraulic modelling of the new meanders to optimise sedimentary balances, the energy dissipation of flows and the diversification of aquatic habitats. This complex technique recreates the natural dynamics of erosion/sedimentation and restores the associated ecological processes.

Recreating the cross-profile : resizing of the minor bed according to hydraulic calculations to obtain an optimal wetted section, with reprofiling of the banks according to variable slopes and development of a functional major bed allowing the controlled expansion of floods. This topographic reconstruction makes it possible to establish a balance between hydraulic capacity and ecological functionalities.

Particle size restoration : reconstitution of a diversified alluvial substrate by adding materials calibrated according to precise particle size curves (gravel, pebbles, blocks) reproducing the natural composition, with the creation of alternating wet-raft sequences and the establishment of a stable but morphogenic bottom armour. Particle size diversity is essential to recreate aquatic micro-habitats.

Diversification of flow facies : development of various hydraulic sequences (rapids, flat currents, pits, counter-currents) by strategic positioning of structuring elements (groynes, deflectors, berms, bottom sills) calculated to generate heterogeneous flow velocities and depths adapted to the requirements of the different target species. This hydraulic mosaic is the foundation of aquatic biodiversity.

Restoration of ecological continuities

Our developments restore essential connectivity: Removal of cross-cutting barriers : dismantling or levelling of obsolete weirs and dams after a geotechnical study of the potential impacts on the stability of the surrounding structures and modelling of the post-intervention equilibrium profile, including management of accumulated sediments and accompanying measures to stabilise the new longitudinal profile. The removal of obstacles is the most effective action to restore ecological continuity.

Fish crossing devices : design and construction of multi-species fishways (successive basin passes, rough ramps, bypass rivers) sized according to the swimming capacities and behaviour of the target species, with precise hydraulic calculations of flows, flow speeds, dissipated power and inter-basin head heights. These complex engineering structures are calibrated to operate over a wide range of flow rates.

Reconnection of hydraulic tenders : restoration of exchanges between the main watercourse and its ancillary environments (secondary branches, lateral wetlands, former meanders) by targeted earthworks, regulated hydraulic structures and/or modification of elevation profiles, thus recreating the mosaic of habitats characteristic of functional natural hydrosystems. This lateral reconnection is fundamental for the life cycles of many species.

Restoration of sedimentary continuity : implementation of alluvial material management systems (sediment traps with release protocols, instructions for the management of flush valves, recalibration of discharge structures) to restore the longitudinal sediment transit necessary for the morphodynamic balance of the watercourse. The balance of the sediment budget conditions the long-term morphological stability.

Ecological engineering of riverbanks and riparian forests

Our plant-based techniques enhance ecological functionalities: Vegetation stabilization of the banks : implementation of combined plant engineering techniques (live weirs, braiding, seedbed and spear, vegetated boxes, cuttings, specific seedings) using native riparian species selected for their root characteristics, their adaptation to local water conditions and their ecological potential. These techniques offer increasing resistance to erosion as the plant develops.

Stratified reconstruction of the riparian forest : planting structured in herbaceous, shrubby and tree strata with a selection of species adapted to their topographical position in relation to the watercourse, respecting local floristic processions and integrating future management constraints and targeted ecological functionalities (shade, habitats, food resources, biological corridors). The structural complexity of the riparian forest multiplies the ecological niches available.

Creation of specific habitats : integration of structuring elements for fauna (anchored stumps, submerged dead trees, boulders, helophytic banks, micro-cliffs) strategically positioned to provide spawning areas, refuges, egg-laying supports or feeding sites for the target species identified during the initial ecological diagnosis. The diversity of micro-habitats directly conditions the species richness of the restored environment.

Fight against invasive species : implementation of specific protocols for the elimination of invasive alien plant species (selective stripping, tarpaulin, repeated mowing, manual uprooting) with secure management of plant waste, traceability of contaminated land and post-work monitoring plans to guarantee the non-recolonisation of restored areas. This preventive control is essential to the ecological success of the project.

Hydraulic and hydrogeological management

Our interventions restore hydrological functionalities: Restoration of flood expansion areas : topographical reconfiguration of the alluvial plains to optimise the temporary storage of flood water, with precise hydraulic modelling of flood areas, mobilizable volumes and effects on flood peak capping, including land acquisition or contractual easements with the owners concerned. These expansion areas contribute significantly to the reduction of flood risks downstream.

Reconnection of the water table and the river : restoration of vertical exchanges between surface and groundwater by removing clogged layers, recreating permeable bottoms and restoring water levels favourable to hyporheic flows, thus contributing to the thermal regulation of the watercourse, the support of low water levels and the natural self-purification of water. These exchanges are a fundamental ecological process that is often neglected.

Flow control : installation of hydraulic devices for dynamic flow management (regulated valves, adjustable thresholds, calibrated weirs) with the development of management protocols adapted to ecological objectives and usage constraints, including automation and remote management for real-time optimization. The fine control of flows makes it possible to achieve precise ecological objectives while respecting anthropogenic uses.

Restoration of associated wetlands : rehabilitation or creation of peripheral wetlands (ponds, hygrophilous meadows, reed beds) hydrologically connected to the watercourse, with prior soil and hydrogeological studies, precise earthworks and establishment of diversified hygrophilous vegetation adapted to local hydrogeochemical conditions. These satellite ecosystems considerably increase the overall biodiversity of the riparian complex.

Advanced technologies and methodologies

Our approach integrates the most efficient technical tools:

Modeled and Design Assisted

2D/3D hydraulic modeling : numerical simulation of flows by specialized software (HEC-RAS, TELEMAC, MIKE) integrating precise topography, differentiated roughness and multiple hydrological scenarios, making it possible to accurately anticipate the hydraulic behavior of the planned developments and to optimize their dimensioning. These templates allow for virtual testing of different configurations before implementation.

Parametric morphological design : scientific sizing of geomorphological characteristics (sinuosity, width, slope, particle size) based on river hydraulics equations and empirical relationships established between hydro-morphological variables, ensuring the dynamic stability of the renatured watercourse. The parametric approach guarantees the functional coherence of the recreated morphology.

Habitat modelling : use of micro-habitat methods (EVHA, ESTIMHAB) combining hydraulic models and ecological preferences of target species to predict the quality and spatial distribution of aquatic habitats resulting from planned developments, making it possible to optimize interventions according to quantified ecological objectives. This approach makes it possible to objectify technical choices according to measurable ecological gains.

GIS and dynamic mapping : integration of multi-thematic spatial data (topography, hydrology, ecology, land) into geographic information systems allowing multi-criteria analyses, evolutionary simulations and production of decision-making cartographic documents facilitating consultation with stakeholders and the temporal monitoring of interventions. These tools constitute the information foundation of the project in all its dimensions.

Specialized earthmoving techniques

Machines adapted to sensitive environments : use of specific equipment with low bearing capacity on the ground (widened crawler excavators, amphibious machines) equipped with precision buckets and high-precision hydraulic systems allowing fine earthworks that respect the environments crossed, with intervention protocols minimizing the impact on fauna and flora. The specialization of technical means is essential in a sensitive ecological context.

Sequential intervention methodologies : organisation of the work according to precise temporal and spatial phasing allowing intervention in optimal hydraulic conditions (low water periods), except for sensitive biological periods (reproduction) and with successive isolation of the treated sections to maintain ecological continuity during the work. This fine planning is fundamental to minimize temporary impacts.

Excavated material management : selective sorting of substrates according to their particle size characteristics and environmental quality, with optimised on-site reuse protocols (reconstitution of alluvial substrates, topographic modelling) or specific disposal channels for polluted or unsuitable materials. The circular economy of materials reduces the environmental footprint of the construction site.

Techniques for preserving biological heritage : implementation of protocols for the protection of pre-existing fauna and flora (safeguarding fisheries, transplants, movements of protected species) with temporary ex-situ conservation facilities if necessary and post-work relocation according to precise as-built plans. The preservation of existing biological capital is an ethical and regulatory priority.

Instrumentation and scientific monitoring

Permanent hydrometric stations : installation of devices for the continuous measurement of hydrological parameters (flows, levels, speeds) with telemetry transmission of data, allowing real-time monitoring of post-restoration hydraulic behaviour and the possible adjustment of developments during the morphodynamic stabilisation phase. This objective data quantifies the hydraulic success of the project.

Physico-chemical monitoring : deployment of multi-parameter probes (temperature, dissolved oxygen, turbidity, conductivity, pH) at strategic points of the restored line, with additional sampling protocols for laboratory analysis of specific parameters relevant to the local context. This monitoring documents the evolution of the quality of the aquatic environment following the interventions.

Standardized biological monitoring : implementation of standardised protocols for fauna and flora inventories (electric fishing, IBGN, IBD, IBMR, phytosociological surveys) before work, then according to an adapted post-restoration chronology, making it possible to objectively assess the ecological gains obtained by comparing them to the initial state and the objectives set. These biological indicators are the ultimate measure of ecological success.

Photogrammetry and Repeated Topography : carrying out high-precision topographic surveys (terrestrial LIDAR, drone photogrammetry) according to the planned frequency to monitor the morphological evolution of the restored watercourse, quantify the erosion/sedimentation processes and analyse the post-restoration morphodynamic trajectory. The documented geomorphological evolution makes it possible to assess the sustainability of the developments.

Applications and project typologies

Our expertise covers all renaturalization contexts:

Restoration of urban and peri-urban watercourses

Specific constraints : interventions in a context of strong anthropization requiring reconciliation between ecological objectives, landscape integration, recreational uses and multiple technical constraints (underground networks, engineering structures, limited land), with particular requirements of public safety and social acceptability. Renaturalization in urban areas is a particularly complex technical and social challenge.

Discovery of buried watercourses : reopening of historically canalized or drained sections with complete recreation of the bed and banks, management of hydraulic constraints (flow capacity, upstream-downstream connections) and urban integration (crossings, accessibility, safety), requiring close coordination with all related urban networks and infrastructures. These iconic projects are radically transforming urban landscapes.

Renaturation of old artificialised canals : ecological transformation of straight channels by diversifying the route and cross-sections in the available right-of-way, with the creation of constrained sinuosities, alternating benches and micro-habitats, while maintaining essential hydraulic functions and integrating urban uses (promenades, recreational areas). These technical compromises require a high degree of design precision.

Landscape and social integration : design of riparian developments promoting citizen appropriation (paths, observation points, educational signage) and landscape quality (greening adapted to the urban context), taking into account the issues of monitoring, maintenance and management of uses in a multifunctional environment. Social acceptance is a key factor in long-term success.

Restoration of agricultural watercourses

Reconciling with agricultural uses : development of projects integrating the maintenance of agricultural functions (drainage, irrigation, watering, crossings) while restoring the ecological and morphological qualities of the watercourse, with land negotiations (widened grassy strips, controlled expansion areas) and possible agronomic compensation. Cooperation with the agricultural world is fundamental for the feasibility of these projects.

Resize Recalibrated Sections : reasoned reduction of oversized sections inherited from historical agricultural sanitation policies, with adjustment of the hydraulic gauge to ecological functionalities while maintaining a drainage capacity compatible with the protection of agricultural land against frequent flooding. This rebalancing requires precise hydraulic modeling.

Restoration of riparian corridors : recreation of functional riparian forests in an agricultural context with sizing adapted to the constraints of exploitation (partial shade, machine access, mechanizable maintenance) and selection of species compatible with riparian uses, including contracts with farmers for the sustainable management of these ecological corridors. The riparian forest is a critical interface between the agricultural environment and the aquatic ecosystem.

Multifunctional buffer zones : development of transitional spaces between cultivated plots and watercourses combining ecological (habitats, corridors), hydrological (flood expansion, runoff filtration) and agronomic (fodder resource, biomass production) functions, with riparian agroforestry systems adapted to local pedoclimatic contexts. These buffer zones optimize the coexistence between agriculture and river ecology.

Forest stream restoration

Specificities of intervention in a forest environment : adaptation of intervention techniques and schedules to the constraints of accessibility, protection of forest soils and preservation of riparian stands, with the use of low-impact methods (cable skidding, residual traffic, temporary access) and coordination with forest management. The ecological sensitivity of forest environments requires special operational precautions.

Ice jam and deadwood management : development of differentiated strategies integrating the fundamental ecological role of woody structures in the aquatic ecosystem (habitats, hydraulic diversification, trophic resources) while managing potential hydraulic risks, with the definition of monitoring and selective intervention protocols. The rational management of dead wood is a major ecological issue.

Restoration of riparian stands : recreation of tiered and diversified riparian forests adapted to the forest stationary context, with the selection of native species resistant to variable water conditions and emerging pathologies, including strategies for adapting to climate change to ensure the sustainability of ecological functions. The evolution of climatic conditions profoundly modified the approach to riparian forestry.

Treatment of discontinuities : identification and resolution of ecological continuity breaks points specific to forest contexts (forest service crossings, stabilization weirs, heritage hydraulic structures) with technical solutions adapted to the constraints of forest exploitation and local heritage issues. The fragmentation of forest watercourses is often underestimated despite its significant ecological impact.

Complete hydrogeomorphological restoration

Complete recreation of the route : design and construction of new river beds according to scientific geomorphological principles, with precise definition of morphometric (width, depth, sinuosity, slope), particle size (composition and structure of the substrate) and hydraulic (speeds, tractive stresses, specific power) parameters ensuring dynamic stability and optimal ecological functionalities. These major interventions completely reset the morphodynamic trajectory of the watercourse.

Restoration of sedimentary processes : reactivation of the dynamics of controlled lateral erosion, solid transport and sedimentation by removing obsolete bank protections, recalibration of upstream solid inputs and creation of mobility spaces allowing the watercourse to regain a self-maintaining morphodynamic balance. The restoration of sedimentary flows is the driving force behind natural river dynamics.

Reconnection of alluvial plains : re-establishment of hydrosedimentary exchanges between the minor bed and the alluvial plain by lowering the banks, removing embankments or creating controlled breaches, allowing beneficial periodic flooding, natural sediment recharge and dynamic rejuvenation of the characteristic alluvial environments. The functionality of the alluvial plain determines the richness of the river ecosystem as a whole.

Adaptive Management : implementation of strategies for the gradual adjustment of interventions based on the continuous monitoring of the responses of the river system, with the prior definition of intervention thresholds, warning indicators and possible corrective measures to accompany the natural evolution of the watercourse towards its new equilibrium. Humility in the face of natural processes guides this evolutionary approach.

Integrated methodological approach

Governance and multi-stakeholder consultation

Our approach systematically includes: Stakeholder analysis : exhaustive identification of the actors concerned (local authorities, State services, riparian owners, users, associations) with a precise mapping of their interests, constraints and levers of action, allowing the development of a consultation strategy adapted to the territorial and human specificities of the project. This preliminary sociological analysis conditions the social acceptability of the project.

Structured participatory approach : organisation of consultative and collaborative processes (thematic workshops, field visits, steering committees, public meetings) according to a methodology adapted to local issues, with the production of specific mediation tools (3D modelling, photomontages, interactive models) facilitating technical appropriation by non-specialist audiences. Collective intelligence substantially enriches the quality of projects.

Environmental pedagogy : development of actions to raise awareness of the ecological functions of watercourses (guided tours, educational materials, targeted training) to explain the multiple benefits of renaturalisation and to transform the often negative cultural perceptions of "wild" rivers. The transformation of social representations is a prerequisite for changes in practices.

Contracting and commitment : formalization of agreements between stakeholders (objective agreements, management protocols, environmental easements) clearly establishing the responsibilities, rights and duties of each party over the long term, with shared monitoring and evaluation mechanisms guaranteeing the sustainability of commitments beyond political temporalities. The legal registration of commitments secures the sustainability of the project.

Integration of regulatory dimensions

Our expertise includes mastery of the legal framework: Environmental procedures : preparation of complete regulatory files (environmental authorisation, water law dossier, impact studies, Natura 2000 impact assessments) integrating all legal requirements with anticipation of sensitive points and rigorous scientific justification of technical choices with regard to normative constraints. The legal solidity of the file secures the implementation schedule.

Land Management : support for the acquisition or land control procedures necessary for the project (amicable negotiations, declarations of public utility, environmental easements) with specific legal expertise on watercourse issues (state-owned property, water rights, access to banks) and integration into local urban planning documents. Land control is often the main limiting factor for ambitious projects.

WFD and SDAGE compliance : precise alignment of the objectives and methods with the requirements of the Water Framework Directive and the applicable Water Development and Management Master Plan, with quantified demonstration of the project's contribution to the achievement of good ecological status and integration into territorial programming (river contracts, SAGE). This consistency with higher planning facilitates public funding.

Management of protected species : anticipation and rigorous treatment of issues related to legally protected species (specific inventories, derogation files, compensatory measures) with specialized ecological expertise to transform these regulatory constraints into opportunities for ecological improvement of the project. The presence of protected species, well managed, generally reinforces the final ecological quality.

Post-restoration monitoring and adaptive management

Our commitment is long-term: Scientific monitoring protocols : development and implementation of multi-indicator monitoring programs (physical, chemical, biological, morphological) according to standardized methodologies allowing objective evaluations, comparisons with other restored sites and scientific capitalization of feedback. These protocols precisely document the post-restoration evolution trajectories.

Analysis of trajectories : expert interpretation of monitoring data to characterize post-restoration dynamics, assess the achievement of initial objectives and identify possible unanticipated developments requiring adjustments, with the production of regular scientific reports and syntheses accessible to non-specialists. This dynamic analysis informs adaptive management decisions.

Evolving management plans : definition of maintenance and intervention strategies differentiated according to sectors and issues, with planning of recurrent operations (vegetation management, monitoring of structures) and exceptional intervention protocols (post-flood, unforeseen problems), including periodic revisions based on monitoring results. Differentiated management optimises the ecological cost/benefit ratio in the long term.

Transfer of skills to managers : in-depth training of the local teams responsible for the restored site (river technicians, technical services) in the specificities of the management of renatured watercourses, with the production of personalised technical guides, in situ support and availability of expertise for further advice. This transfer of know-how conditions the sustainability of the ecological benefits obtained.

Multidimensional benefits of renaturalization

Ecological benefits

Restoration generates significant gains for biodiversity: Aquatic habitat diversification : multiplication of available ecological niches thanks to the rediscovered variety of substrates, depths, flow velocities, shade and shelter, allowing the resettlement of extinct sensitive species and the significant increase in biodiversity indices (species richness, Shannon indices, equitability). Recreated structural complexity is the foundation of biological wealth.

Restoring ecosystem functionality : restoration of fundamental ecological processes (biogeochemical cycles, trophic chains, population dynamics) allowing the emergence of a self-sustaining ecosystem, resilient to disturbances and capable of sustainably ensuring its ecological functions without regular human intervention. The regained functional autonomy marks the ultimate success of a restoration.

Strengthening ecological continuities : reintegration of the restored watercourse into larger-scale ecological networks (blue belt) facilitating biological migrations, genetic mixing and natural recolonisation, with positive effects extending well beyond the directly restored linear. The ecological benefits are thus propagated throughout the connected river network.

Climate change adaptation : creation of ecosystems that are more resilient to extreme events (floods, droughts, heat waves) through the restoration of refuge areas, the diversification of habitats and the restoration of more buffered thermal regimes, offering species better capacities to adapt to ongoing climate changes. This ecological resilience is becoming crucial in the context of accelerating global change.

Hydrological and safety benefits

Renaturalisation improves flood risk management: Dynamic flood slowing : natural attenuation of flood peaks by increasing roughness, restoration of sinuosities and reconnection of lateral expansion zones, allowing temporal spreading of flood hydrographs and reduction of peak flows downstream, with quantifiable beneficial effects on protected inhabited areas. This natural regulation is an alternative or a complement to conventional hydraulic structures.

Morphodynamic stabilization : reduction of uncontrolled erosion phenomena by restoring natural sedimentary balances and distributed energy dissipation, limiting the risks of regressive erosion, incision of the bed or destabilization of riparian infrastructure. The new morphodynamic balance provides more durable stability than perishable artificial protection.

Low-water support : improvement of low-water flows by slowing down flows, recharge of alluvial aquifers and increase in groundwater-river exchanges, contributing to the maintenance of minimum biological flows during dry periods and to the reduction of water stress on ecosystems and uses. This hydrological regulation function becomes critical in the face of increased droughts.

Prevention of the risk of ice jams : preventive management of woody accumulations by restoring a balanced and maintained riparian forest, creating controlled deposition areas and designing suitable crossing structures, reducing the risk of sudden obstruction and flow breaks during flood episodes. Preventive management of ice jams is more effective than curative interventions.

Socio-economic benefits

Renaturalization projects generate multiple benefits: Territorial enhancement : substantial improvement in the attractiveness of the restored riverside areas for residents and visitors, with the development of new recreational uses (walking, naturalist observation, recreational fishing) and differentiating tourist opportunities enhancing the image of the territory and its living environment. Renatured watercourses are becoming major territorial assets.

Enhanced ecosystem services : optimisation of the benefits provided free of charge by the natural functioning of the watercourse (self-purification, local climate regulation, fishery resources, landscape value) generating substantial savings compared to equivalent artificial technical solutions. Economic analysis of ecosystem services generally demonstrates the cost-effectiveness of restoration investments.

Reduced maintenance costs : significant reduction in costly curative interventions (post-flood repairs, dredging, emergency protection) thanks to the restoration of self-regulating operation requiring only monitoring and light maintenance, with optimization of public management expenditure over the long term. The return on investment is usually seen after a few years of operation.

Local Skills Development : creation of specialised technical expertise within local management structures, with the development of the skills of territorial teams on innovative approaches that can be transferred to other projects, constituting technical and human capital that can be used beyond the initial project. This technical capitalization sustainably enriches the territorial engineering available locally.

Our commitment to quality

For each renaturalisation project, Braux undertakes to:

apply the most rigorous scientific methodologies in analysis and design
use only techniques and materials that respect the environment and living things
ensure full transparency of decision-making processes and technical choices
ensure exhaustive traceability of the interventions carried out and their results
Maintain a permanent scientific watch to integrate advances in the field

The renaturalization of waterways represents a major environmental investment with multiple benefits extending well beyond the simple perimeter of intervention. By entrusting the design and implementation of these complex projects to Braux, you ensure an approach that integrates technical excellence, scientific rigour and ecological sensitivity, generating sustainable restorations that combine the reconquest of biodiversity, improvement of hydraulic safety and territorial enhancement. Contact our specialized team for an initial diagnosis of your watercourse and an analysis of the restoration potential, including a technical feasibility study, budget estimate and operational programming adapted to your specific context.