Expert in
Large Wood Dynamics & Blockage Risk
Analyses and customised protection concepts for authorities, infrastructure and stakeholder – decision‑making for climate‑adapted flood risk management.
Smart solutions for rivers
Engineering office for water management
When large wood becomes a risk…
Large‑wood blockages are among the most frequent triggers of unexpected flooding and damage during high flows. Robust quantification and upstream prevention (at the source) creates planning certainty – from risk assessment to the design of protective measures.
What is large wood (driftwood)?
What is large wood (driftwood)?
Large wood is a natural and valuable component of rivers. It creates diverse habitats, supports river morphology, promotes biodiversity and can stabilize the riverbed. It can also improve flow dynamics by creating hydraulic diversity and influencing sediment processes.
During floods, however, this natural element can become a significant hazard factor.
Why does large wood become problematic during floods?
During heavy rainfall and floods, wood from riparian zones and the catchment is mobilized and transported downstream with high dynamics. At bridges, culverts and other constrictions it can accumulate quickly and form massive blockages.
The consequences can be severe:
- rapid backwater and unexpectedly rising water levels
- flooding of settlements and critical infrastructure
- significant additional loads on structures
- surge‑like waves if a blockage fails suddenly
Such developments often occur at short notice and with high dynamics – especially where the large‑wood potential has not been assessed systematically in advance.
Why prevention is decisive
Large‑wood risks are not random. They result from catchment conditions, river structure and the configuration of structures. If these interactions are not analysed early, even well‑dimensioned protection measures can reach their limits.
A forward‑looking assessment of large‑wood potential is therefore not an add‑on, but a key safety factor for municipalities and critical infrastructure.
Conclusion
Large wood is ecologically valuable – but during floods it can amplify damage. Without a sound risk analysis, blockages can lead to significant economic losses within a very short time.
Engineering Office Spreitzer supports the systematic assessment of large‑wood risks and develops robust strategies to minimise hazards – before a natural element becomes a safety‑critical problem.
… it requires:
Risk analysis and potential assessment
Systematic assessment of large‑wood potential in the catchment and identification of sensitive areas with elevated blockage risk. The goal is to detect hazards early and assess them realistically.
Targeted protection strategies
Integration of potential large‑wood impacts into the planning and design of hydraulic structures to effectively minimise risks to structures and settlement areas.
Operations and preparedness management
Continuous monitoring of critical reaches and coordinated preparedness strategies increase operational safety and reduce damage potential during events. Integrated large‑wood management connects safety requirements with ecological objectives.
Reducing flood risk before an event occurs
Flood protection starts in the upper catchment: rainfall is retained and infiltrated at the source to mitigate runoff and effectively reduce peak discharge on downstream river systems.
Flood protection starts in the catchment
Flooding does not start in the river channel – it starts in the catchment. Where rainfall hits the ground and runoff processes form, the conditions for later impacts are set.
Proactive flood prevention therefore starts early: targeted measures in the catchment can effectively reduce peak flows and sustainably relieve downstream rivers and infrastructure.
What matters is not one single measure, but the coordinated interplay of many factors across the catchment. Especially micro‑scale, decentralised solutions can have a noticeable effect on the overall system when designed well.
This is where an integrated perspective matters:
Only by analysing runoff dynamics, terrain, land use and hydraulic interactions holistically can effective and economically sound prevention strategies be developed.
Engineering Office Spreitzer supports authorities, infrastructure operators, professional bodies and landowners with sound catchment assessments and develops tailored concepts for sustainable flood prevention – forward‑looking, system‑based and focused on long‑term safety.
Analysis of catchment and runoff processes
Topography, land use and natural boundary conditions largely determine how rainfall turns into runoff. Only a systematic analysis of these interactions enables early risk detection and robust prevention strategies.
Decentralised retention and infiltration
Sustainable flood protection relies on retention and infiltration at the source. Decentralised measures in the catchment reduce peak flows and relieve downstream rivers and infrastructure. Potential large wood should also be considered early and, where necessary, retained in a controlled manner to minimise later risks.
Integrated implementation and stakeholder coordination
An effective protection concept is not created by isolated measures, but through coordinated action across the catchment. Municipalities, infrastructure operators and landowners all contribute. Only coordinated strategies create a noticeable and sustainable relief for the overall system.
Contact Person
Engineering expertise with international research and project experience in flood protection – specialised in large‑wood dynamics and blockage processes in rivers.
Dipl.-Ing. Gabriel Spreitzer, Ph.D.
Founder & CEO – Consulting Engineers Spreitzer (Environmental Engineering and Water Management)
Zanitzberg 15, 8850 Metnitz · Tel. (+43) 0681 8113 1664 · office@ib-spreitzer.at
Expertise
SmartWood_3D is the scientific foundation of our practice. Developed by Gabriel Spreitzer during his doctorate and funded by the European Commission (EU Horizon). It enables methods for quantitative large‑wood risk assessment and provides evidence‑based decision support for authorities and responsible stakeholders.
Internationally established expertise
Dipl.-Ing. Gabriel Spreitzer, Ph.D. specialises in large‑wood transport and blockage dynamics in flood contexts.
- Civil Engineer (Geotechnical & Hydraulic Engineering) – Graz University of Technology (Austria)
- Ph.D. at the University of Auckland (New Zealand)
- Postdoc at ETH Zurich (Switzerland)
- Marie Curie fellowship awarded by the European Commission (EU Horizon)
His international research focuses on quantifying large‑wood transport, blockage mechanisms and their hydraulic interactions with river infrastructure. This scientific specialisation forms the foundation of our practical work in large‑wood risk management and flood prevention.
Photogrammetry & 3D documentation
Complex large‑wood accumulations and blockages are captured, reconstructed and analysed in 3D.
The developed methodology enables:
- volumetric quantification of blockages
- objective assessment of hydraulic relevance (e.g., blockage porosity / permeability)
- capture of structural arrangement of wood elements (“key logs”)
- event documentation before and after flood events
- robust basis for planning and prioritisation
turns visual observations into measurable data.
Decisions are based on quantitative data and structural analyses – not on assumptions or rough estimates.
Sensor-based systems – SmartWood_3D (optional early-warning)
Large‑wood transport follows distinct dynamics – mobilisation, transport and deposition processes that can be described physically.
Key is the precise measurement and understanding of these processes during flood events.
Sensor-based systems enable:
- measurement (quantification) of mobilisation and transport during floods
- recording impact forces of transported wood at structures
- analysis and reconstruction of pathways and trajectories along critical reaches
- identification of preferred deposition and concentration zones
The data provides robust insight into real system dynamics. This allows large‑wood fluxes to be influenced upstream of critical constrictions and retained early where required.
At the same time, sensor data supports the correct sizing and placement of retention and guiding structures. Measures are not applied generically, but designed from real transport dynamics.
This turns observation into controllable, climate‑adapted prevention.
From research to practice
Our experience shows: transport dynamics are not random. Blockages result from specific transport and deposition processes.
They are shaped by catchment conditions, discharge, transport dynamics and the configuration of structures.
During floods, moments can decide between backwater, inundation and structural overload.
Unassessed large‑wood risks are among the most underestimated amplifiers of damage in river systems during floods.
A sound understanding of large‑wood transport dynamics is decisive for targeted retention concepts and avoiding uncontrolled deposition. We provide clear decision support for:
- die Auswahl technisch wirksamer und wirtschaftlich aber auch ökologisch vertretbarer Maßnahmen which locations/structures are critical
- prioritised mitigation (where action is truly needed)
- correct sizing and placement of retention and guiding structures
- identification of preferred deposition and concentration zones
- assessing existing infrastructure for blockage susceptibility
- optimising operations, maintenance and monitoring strategies
- transparent communication to authorities, operators, funding bodies and landowners
The transition from research to practice is systematic: scientific models are validated with real measurements, event analyses are translated into planning parameters, and theoretical insights become actionable engineering decisions.
Scientific depth is translated into concrete, implementable strategies.
Services
Consulting engineering office – water management & river engineering. Focus: large‑wood and flood prevention based on clear, robust decision evidence.
Wir unterstützen Behörden, Infrastrukturbetreiber, Fachverbände aber auch private Grundbesitzer bei der Bewertung der zu erwartenden Schwemmholzfracht sowie dem Verklausungsrisiko
during floods and support the development of tailored prevention measuress- und Schutzkonzepte.
Concept & detailed studies
Sound concept and detailed studies as a robust basis for prioritisation, investment decisions and long‑term, climate‑adapted flood safety.
Risk analysis & measures planning
Systematic assessment of large‑wood and flood risks – from the upper catchment to critical infrastructure.
Derivation of technically effective and economically viable protective measures.
Large‑wood potential & blockage assessment
Identification of critical constrictions and assessment of real blockage risks at bridges, culverts and river infrastructure.
Clear decision support for municipalities and operators of safety‑critical infrastructure.
Documentation, monitoring & event analysis
Objective documentation before and after flood events, 3D analysis, and structured evaluation of events.
Transparent evidence for planning certainty, optimisation and liability relevance.
Decentralised retention & catchment concepts
Development of effective strategies for retention and infiltration where floods originate.
Holistic perspective from micro‑scale to the main river.
Additional services
Support across water management tasks – from planning and assessment to technical supervision and expert opinions.
References
Selected focus areas and research practice – curated, traceable and suitable for authorities.
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Contact
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