Seaside Akiya and the Flood Question: Reading Coastal Flood and Tsunami Zones

A buyer asked us a question that many people have: can I have a house by the sea, but outside the flood zones? An akiya (an empty home in Japan) by the water is a fine thing to want. The honest answer is "sometimes, and you need to know which map you are looking at".

This guide only covers the coastal angle. For how to read the hazard rows on a listing, see how to read a Japanese hazard map. For the wider question of risk and the building itself, see is it safe to buy an akiya. We do not repeat them here.

Which checks matter by the sea?

Three government layers matter near the coast. They are not loaded everywhere, and that is the main thing to understand.

• River flood. Whether the home's map point is inside a designated river flood area, and the expected depth. Loaded for every prefecture we list. It is a river map, not a sea map.
• Tsunami. Whether the point is inside a designated tsunami inundation zone, and the expected depth. Loaded for all coastal prefectures except Kagawa, where no government file is published.
• Storm surge. Whether the point is inside a designated storm-surge zone. This only exists where a prefecture has published a study, so it covers a small part of the coast.

A fourth fact, distance to the coast, is loaded for two prefectures only. More on that below.

How patchy are the checks?

Near the coast, "Not checked" is common, and it never means clear. The hazard-map guide explains why a home can be not checked.

As of 15 October 2026, across the 8,494 live homes for sale on Engawa:

These are totals for all of Japan, inland homes included. They are not counts of seaside homes.

Storm surge is the clearest example. Only 340 homes sit inside an area a prefecture has studied. For the other 8,154 there is no result, and many listing pages show no storm-surge row at all. Kagawa is the one coastal prefecture with no government tsunami file, so tsunami is not checked there.

Where is storm surge checked?

Homes in 14 prefectures sit inside a published storm-surge study. This is how many live homes we could check, and how many fell inside a zone.

Read this as a map of where the question can be answered, not as a ranking of danger. Of the 340 homes checked, 142 are inside a zone. Where no study exists, the question is open.

Where do we know how far the home is from the sea?

Only in Kyoto and Kagoshima. In those two prefectures a listing shows a "Coast" row, for example "About 0.1 km from the coast". Everywhere else the distance is not loaded, and the absence of a row says nothing about how close the sea is. The figure is a straight line to the nearest mapped coastline, rocky or sandy alike. It does not mean a beach.

That gives a real, if narrow, answer to the buyer's question. As of 15 October 2026, 166 live homes are within 3 km of the coast, in Kyoto (53) and Kagoshima (113). Of those, 137 are clear on both river flood and tsunami.

Do not read that as a number for Japan. Outside those two prefectures there is no coast figure, which is not the same as zero.

You can see the same filter on Explore. Try near the coast, or near the coast and outside both flood and tsunami zones. The second shows 137 homes. Browse the prefectures directly at Kyoto and Kagoshima.

Tsunami zones sit close to the coast

Kyoto and Kagoshima together have 491 live homes. 32 have no coast figure. 29 of those 32 are also among the 31 homes not checked for flood or tsunami, and 2 more homes in the 3 to 10 km band are not checked either. That leaves three bands close to the coast, shown here, then 146 homes at 10 to 50 km and 21 over 50 km (292 + 146 + 21 + 32 = 491):

The tsunami pattern is clear in this data: all 13 homes in a tsunami zone are within 1 km of the coast. That is a pattern in two prefectures, not a rule for Japan.

River flood is different. It does not follow the coast: homes 10 to 50 km from the coast (146 of them) have 17 inside a flood zone, more than any band above, and the 21 homes over 50 km have 4. A home 2 km from the sea can sit beside a river inside a flood zone.

What does "clear" leave out by the sea?

The hazard-map guide covers what a flood result means. The coastal point is this: a river flood result is a river map, not a sea map. A home can be outside a river flood zone and still be in a tsunami or storm-surge zone. And a "Checked, clear" on tsunami is a map result, not a promise. Waves, high tides and heavy rain can reach places the national maps do not cover; the official map for your address is at disaportal.

Two homes show how different the results can be. A home in Miyazu, Kyoto, about 0.1 km from the coast, sits in both a flood area and a tsunami inundation zone, and has no storm-surge row because no study covers that point. A home in Akune, Kagoshima, also about 0.1 km from the coast, reads "Checked, clear" on both. That is why we show each home and do not describe a coast.

Which questions should you ask?

These points are not ours to advise on. Ask the town office, the bank through the original listing, or a licensed agent.

• Does the town publish a hazard map for this address? The official map is the one that counts. The national portal is disaportal.
• Is the house inside a tsunami or storm-surge area, and does the town have an evacuation route for it?
• What does the town say about flooding from small streams and drains, which the national river map does not cover?
• Can insurance be arranged for this house? Ask an insurer or a licensed agent. We do not advise on insurance.
• What condition is the building in? A surveyor answers that. Our guide to old earthquake rules and akiya condition says who checks a house.

Looking for something other than the coast?

If you are weighing the sea against the hills, see mountain and river country akiya. If the real question is distance to the city, see akiya within reach of Tokyo.

How we know this

The flood layer is the government's designated river flood data (FY2024). The tsunami layer is the national tsunami inundation data (FY2016). Storm surge uses the government's published hazard-map tiles. The coast distance uses the national coastline data (FY2006), loaded for Kyoto and Kagoshima. All counts are live homes on Engawa as of 15 October 2026 and will change as the catalogue changes. A hazard result on Engawa is a first look from government maps. It is not a survey, and it is not advice.

Frequently asked questions

Can I have a house by the sea outside flood zones?

Sometimes. In Kyoto and Kagoshima, where we hold coast distance, 137 homes within 3 km of the coast are clear on river flood and tsunami. Clear means a map result for those two checks. It is not a promise, and storm surge is not checked for those homes.

Does "outside a flood zone" mean the house will not flood?

No. The maps cover designated rivers only. Small streams, drains and heavy rain on flat ground may not be on them.

If a listing shows no storm-surge row, is it safe from storm surge?

No. The row is absent where no study exists. That is "not checked", not clear.

Why can't I search all of Japan for seaside homes?

Because we hold coast distance in two prefectures only. Outside them, browse the prefecture pages and read each home.

Ready to ask?

Found a home by the sea that you want to know more about? Open the home and use "Enquire about this house". A founder replies by email, and it is free to ask. If an estate agent handles the sale, you can also ask Koryoya, our listed agent, to help in English: your enquiry reaches us first, and reaches Koryoya only after you confirm your email and we forward it. Say in the message that you want flood, tsunami and storm-surge questions put to the town or the agent. See who is listed on the agents page.