River waves · building, running, surfing

Can a wave create habitat?

Surf structures change water bodies – that much is certain. But in which direction? In the sea, artificial surf reefs have been colonised by algae, fish and invertebrates; on rivers, some wave projects advertise ecological enhancement, while studies elsewhere warn of new barriers to fish migration. This page sorts out what is documented – and what we make of it for the Rems: no promises, but a testing programme.

What artificial surf reefs in the sea show

The two best-studied surf reefs lie in the sea, not in rivers – but they show how to answer the question seriously: by looking for years.

Narrowneck (Gold Coast, Australia): built around 2000 from sand-filled geotextile units, for coastal protection and surfing. Surveys documented macroalgae across large parts of the reef surface, along with fish, sponges, sea squirts, sea urchins and soft corals. At the same time, the scientific comparison with natural reefs was sobering: colonised, yes – but the natural reefs remained more diverse. An artificial reef does not replace a natural one. Members of our initiative have seen the Gold Coast and its reef projects for themselves; we will add impressions and pictures from there once they are prepared.

Boscombe (England): built in 2009 as Europe's first artificial surf reef – a disappointment as a surf project, instructive as an ecology experiment. A study covering 2009–2014 counted 180 taxa, among them 132 invertebrate and fish species and 48 algae, with a clear succession of colonisation. However, eleven of the 180 taxa (around 6 per cent) were non-native species – a higher share than on natural reefs. The researchers' conclusion is a lesson in caution: the contribution to biodiversity may be considered positive – provided no negative impacts are detected on the natural reefs.

The lesson: colonisation is the normal outcome when you place hard substrate in water. Whether that adds up to an ecological gain is decided by comparison with what was there before – and that only shows after years.

And in a river?

River waves are not reefs: in a river, what counts is variety of flow, substrate, pools, refuges – and above all passability for migrating fish. The examples span the whole range:

• Bend Whitewater Park (Oregon): there, a previously impassable dam was rebuilt into a park with separate zones for surfing, fish passage and habitat – an improvement in migration compared with the old state. Important: this advantage does not transfer to the Rems, because at the planned wave site there is no barrier that a wave could remove.
• Fuchslochwelle (Nuremberg) and Leinewelle (Hanover): combine the wave with a fish pass or "eco-pass" and near-natural bank design; the ecological assessments played a central role in the permitting procedures. Independent before-and-after measurements of a net ecological gain are not known to us so far. → Case study Fuchslochwelle · → Case study Leinewelle
• Blackforestwave (Pforzheim): chooses its site in an existing channel to avoid interventions in the river – avoidance as the concept, not retrospective enhancement. → Case study Blackforestwave
• The warning from Colorado: hydraulic model studies of whitewater parks (Gore Canyon among them) found that the built structures can drastically narrow the modelled migration corridors for fish – high velocities, shallow depths and pinch points act as a barrier despite an attractive wave. These are model values, not measured ascent counts – but a clear warning.

Our position for the Rems

For the Remswelle, unchanged: fish passage is a condition, not a bargaining chip. At the planned site the Rems flows freely today – so a wave cannot "unlock" anything there; it must simply not make anything worse. We make no statements about a wave's effect on passability; that is for the feasibility assessment and its specialists. → Weirs and fish passage on the Rems · → Permitting a river wave

The honest research question is therefore not "does the wave help the river?" but: can a wave in an already passable river create additional habitat while passability is fully preserved? Conceivable routes run through structure-rich zones outside the surf area – gravel, pools, refuges. Whether that holds at the actual site, nobody can seriously say today.

What we want to test

Instead of promising, we propose to measure – in this order:

1. Document the before state: fish species, invertebrates, habitats, flow, substrate at the planned site – before anything is built.
2. Use the step at the Vogelturm as a study case: at the small sill before the Remsknie we have long observed strikingly many sticklebacks and crustaceans – more than along uniform stretches. The alternation of fast and calm zones, hiding places and oxygen input can explain that. But beware the quick conclusion: many animals in one spot prove neither more species nor a better overall state. So we want to count – same method, same season, at the step, along smooth stretches and at the future wave site, together with flow, depth, substrate and temperature.
3. Model the hydraulics of the planned wave, especially at low water and during surfing, and have every design variant checked for passability and possible additional habitat.
4. Learn from the others: request and evaluate the landscape management plans and any ecological follow-up surveys from Nuremberg and Hanover.

Frequently asked questions

Does a surf wave automatically create new habitat?

No. What is documented is that new structures in water get colonised – in the sea as in rivers. Whether that becomes a net gain for the water body depends on the prior state, the design and passability, and only shows over years. The only serious approach is to measure before and keep measuring after.

Does the Remswelle remove a migration barrier, as happened in Bend?

No – there is none at the planned site. That is why the Remswelle cannot and will not advertise an "improvement in passability". Its yardstick is stricter: fully preserving today's free-flowing state.

Why count sticklebacks at the Vogelturm, of all places?

Because there you can see in miniature what the large question is about: a step with varied flow visibly attracts life. Whether that means "more animals" or "more species", and what it implies for a planned wave, can only be settled by systematic counting – which is exactly what we intend. It is our own observation, labelled as such.

Were members of the initiative really at the Australian reefs?

Yes – as surfers, members of the initiative travel the world and took a close look at how Australia combines coastal protection, surfing and reef habitat on the Gold Coast. Such impressions replace no studies, but they sharpen the questions we put to studies.

Sources: Herbert, R. J. H. et al. (2017): Epibenthic and mobile species colonisation of a geotextile artificial surf reef (Boscombe), PLOS ONE 12(9): e0184100 · Studies on the Narrowneck reef (geotextile reef communities; Marine Ecosystem Enhancement, Narrowneck case study) · Bend Park & Recreation District: Bend Whitewater Park, 2025 condition report · Richer et al.: Making Waves – Effects on Fish Passage (River Research and Applications, DOI 10.1002/rra.70069) · Nürnberger Dauerwelle: Fuchslochwelle project pages · Administrative Court of Hanover: decision on the Leinewelle · Blackforestwave: wave and environmental concept · Own observation by the initiative (sticklebacks at the Vogelturm, labelled) · → Wildlife of the Rems

Last updated: 15 October 2026 · Initiative Remswelle