Paddling with the Sea-Horse*

Sea-level rise is one of the inevitable and inexorable results of climate change.  Melting ice and increased ocean temperature mean a steady increase in sea levels over time.  Depending on the emissions scenario, global average sea levels could rise anywhere between 0.26m and 0.82m by 2100 with further rises after that.  This in itself is enough to inundate a lot of coastal environments – beaches, coastal wetlands, even whole islands.  Various low-lying island nations are facing the prospect of their entire nations becoming uninhabitable in the coming century – this is why the Pacific Islands Forum has been so adamant about the need to limit the effects of climate change.

If the scale of the rise looks small to you, remember that about 80% of Australians live within 50km of the coast, so this is not a trivial fringe issue – for instance a 0.8m rise would see thousands of homes and businesses in Brisbane experience water on their property at high tide. This is also not the full story - storms and cyclones can produce tidal surges which push the water far higher, and as coastal environments are inundated these surges will push further inland, inundating places that were once safe.  In addition, higher sea levels interact with river flooding – floods coming down-river meeting higher tides washing up-river provide peak flood conditions.    Both housing and infrastructure are likely to be affected by sea level rise over coming decades – surf clubs, beach-front cafes, canal developments and beach-side houses, as well as properties in places you might not think could be affected. 

Preparing for sea level rise is different from extreme heat, bushfire and flood – if your property is being inundated by rising seas, there’s not a whole lot you can do about it as a property owner aside from abandon the site.  Rather, the key adaptation measures need to come from government authorities since they require action at a bigger scale than the individual property owner.

Predicting Sea Level Rise

We have some good resources on how much the sea might rise in different scenarios, and what this will mean for coastal inundation.  However, this is not always easy to interpret.  In an ideal world, your local government’s planning scheme would clearly outline the areas where there was inundation risk, and it’s really worth checking if they have this.  Sadly, you can’t always rely on this – many coastal Councils are struggling to keep up with this issue and it is hotly contested as the owners of coastal land lobby hard to be allowed to develop it, future sea level rise or not.  This means if you are considering building on coastal land you need to do your own due diligence.

In the resources below I’ve listed two sources of mapping information on risks of sea level rise.  I like the Coastal Risk Australia one which provides an interactive mapping tool which you can use to zoom in to specific locations to see the inundation risk under different climate scenarios.  You’d like to think we can get to the point where the ‘low emissions’ scenario is the one we end up living with, but you would be prudent not to plan for that in the current political environment. 

The information these maps are based on is fairly technical and I’m not confident that I fully understand it.  One thing that is clear is that the maps depict mean sea level rise, so they don’t take any account of either storm surges (where of course the water will go higher) or flooding (likewise).  This means that both predicting the impact of sea level rise in a particular location, and deciding what to do about it, requires the kind of detailed technical knowledge possessed by coastal engineers and planners, and as housing organisations we’re very much dependent on them doing their jobs well.

Adapting to Sea Level Rise

CoastAdapt outlines a framework for adapting to sea level rise which I’ll do my best to summarise here.  One of the advantages for us in dealing with this issue is that we have time.  Unlike heat, fire and floods which are on us already, sea level rise is coming slowly and most of it remains in the future.  (Note that this is not the case everywhere – for instance, some of the islands in the Torres Strait are facing issues with sea level rise right now and need quick action).  Of course this means that there’s a risk that politicians with three- or four-yearly elections will just kick the can down the road, but if we start planning now we can be well and truly ready as the seas come up. 

With this in mind, CoastAdapt recommends what it calls a ‘pathways approach’ where hazards are identified along with adaptation options, and then various trigger points are identified at which action would need to be taken.  Hence, communities would be progressively adapting over time rather than rushing to respond in a crisis.  Now, wouldn’t that be nice!

There are then five different ways governing bodies can respond to sea level rise.

1. Avoidance – for instance, not building new housing or infrastructure where you know there will be future inundation.

2. Managed retreat – accepting that something will need to move and shifting it in a timely way before problems arise.  This might include, for instance, replacing run-down sea-front infrastructure in safer locations rather than rebuilding in situ.

3. Accommodation or limited intervention – in some locations, the best options will be just to let what happens, happen (these of course are not areas containing human habitation!) with perhaps some conservation efforts to preserve remnant ecosystems.

4. Hold the line – take steps to combat the effect of sea level rise by, for instance, building sea walls or drainage systems.

5. Loss acceptance – in some cases, there won’t be much anyone can do and we just have to take the hit, hopefully collectively rather than individuals in vulnerable locations.

There are then four different types of tools which we could use as appropriate, realising that we need the right tool for the right situation.

• Planning options to help set out what to build where – this includes locating new development in lower-risk areas or mandating minimum floor heights (for instance, by ensuring buildings are lifted up on piles above the high tide line).

• Engineering solutions, like building sea walls and levees, installing drainage systems, lifting key infrastructure above the expected water level, dredging of estuaries and so forth.

• Ecosystem options – these are oriented towards protecting and/or restoring habitats and endangered species. 

• Social, community and educational options are essential wrap-arounds for all the other options and include raising local awareness of sea level rise, engaging community in developing responses, drawing on Indigenous knowledge, building community resilience and enabling exchange and learning between communities.

They then have a detailed set of implementation resources including a template for planning adaptation response called ‘Coastal Climate Adaptation Decision Support’ (C-CADS).  This provides a detailed, systematic process for planning, implementing and evaluating responses. 

As I mentioned, all of this is at the community and government level.  As a housing organisation the best you can do is stay abreast of what your local government authorities are doing on this issue, assess potential risks to your own properties (and select future projects carefully) and collaborate with planning initiatives focused on adaptation. 

Resources

CoastAdapt has a comprehensive suite of resources on the science of sea level rise, predicted sea levels and possible adaptation measures.  I’ve relied heavily on their research for this article.

For mapping sea level scenarios, CoastAdapt has a series of maps which you can check out here .  However, I find the one developed by Coastal Risk Australia, which uses the same data, easier to use as it’s more interactive and lets you explore different scenarios at quite a fine-grained local level. 

The adaptation section draws on CoastAdapt’s adaptation resources – Understand Adaptation and Undertake Adaptation. https://coastadapt.com.au/undertake-adaptation

*You might think that sea-horses, which as you know are actually fish not horses, would be happy about sea level rise or at least OK with it. However, seahorses live in shallow coastal habitats like mangrove swamps and sea-grass beds which are threatened by sea level rise, and coral reefs which are in imminent danger from the other effects of climate change. So honestly, if they could talk they would tell us to cut our emissions urgently.