We overlaid the registered coordinates of lodging properties in the Shirahama Onsen area of Shirahama Town, Wakayama (around Shirarahama Beach, Yuzaki and Tsunashirazu) on the tsunami inundation zones designated by Wakayama Prefecture. The sample covers 132 properties with 3,040 rooms for which MetroEngines Research could confirm selling prices for stays in September–November 2026. Of these, 57 properties with 1,101 rooms (36.2% of rooms) sit inside the projected inundation zone. Rooms in areas with a projected inundation depth of 3m or more total 1,011, or 33.3% of the sample. By contrast, properties outside the zone have a higher median estimated settled ADR, and more than 80% of rooms at properties opened since 2017 are located outside the zone. This article tallies the distribution by inundation depth band and its relationship with property size, property type, rates, zoning and land prices, and sets out the design, insurance and BCP issues to consider when rebuilding or developing new properties.

Key Points — Inundation Zones Concentrate on the Flatland Behind Shirarahama; Higher-Priced Properties Sit on the Terraces

We start with the conclusions. First, roughly one-third of the rooms at lodging properties in the Shirahama Onsen area lie in zones with a projected inundation depth of 3m or more. This reflects the historical pattern in which onsen ryokan and minshuku (family-run guesthouses) clustered on the flat town area behind Shirarahama Beach and the lowlands along Tsunashirazu Bay. Second, the intuition that “the higher-priced seafront properties are the ones most exposed to inundation” is not supported by the data. The median estimated settled ADR is ¥19,200 for properties outside the zone and ¥10,700 for those inside, with many high-priced ryokan and resorts located on the coastal terraces from Yuzaki to Senjojiki. Third, newer supply increasingly chooses sites outside the zone. Of the 930 rooms at properties opened since 2017, only 170 (18.3%) are inside the zone, a marked decline from properties opened in 2016 or earlier (44.4%).

From an investment perspective, existing properties inside the zone enjoy the locational value of being at the heart of the onsen town and right next to the beach. When rebuilding or undertaking major renovations, building vertical evacuation capacity, placing power-receiving and transformer equipment on upper floors, structuring insurance and incorporating a BCP into the business plan can help preserve that locational value over the long term. Terrace sites outside the zone have been chosen to absorb new supply, and their price levels back that up. The figures are reviewed in turn below.

Scope and Method

The study area is a 3km radius centered on the core of Shirahama Onsen in Shirahama Town (33.68°N, 135.355°E). This radius covers Shirarahama, Yuzaki, Senjojiki, Tsunashirazu, Higashi-Shirahama and part of Katata. MetroEngines Research’s property master lists 190 properties with 4,156 rooms in this radius as of 2026, based on opening and closing dates. Because this includes properties that are closed or whose sales activity could not be confirmed, this article tallies the 132 properties and 3,040 rooms for which selling prices could be confirmed for stays in September–November 2026.

The tsunami inundation projection was obtained from the public data of the MLIT Real Estate Information Library in map-tile units (zoom level 15), yielding 3,786 inundation polygons within the tiles where the sampled properties are located. We determined which inundation-depth polygon contains each property’s registered coordinate and tallied the number of properties and rooms by depth band. Note that the tsunami inundation projection is an official government projection assuming a maximum-class tsunami and does not indicate when or how often such an event will occur. The tallies in this article are intended to characterize locations and do not assess the safety of any individual property.

Properties and Rooms by Inundation Depth Band — 757 Rooms in the 5m-Plus Band

By depth band, the largest group is outside the zone, at 75 properties and 1,939 rooms (63.8%). Inside the zone, the 5m-to-under-10m band is the largest at 28 properties and 757 rooms, followed by the 3m-to-under-5m band at 20 properties and 254 rooms. The shallow bands from 0.3m to under 3m total just 9 properties and 90 rooms. In other words, in Shirahama Onsen most properties inside the inundation zone sit not on its “shallow edges” but in its “deep core.” The flatland behind Shirarahama is low-lying, so properties that fall within the zone tend to fall into the deeper bands.

The skew of the distribution toward deeper bands bears directly on design policy for rebuilding and renovation. The table below shows how the number of properties and rooms in zones at or above a given depth changes as the threshold moves from 0.3m to 5m. Even if raising floor levels or moving equipment to upper floors could address inundation of up to 1–2m, the rooms remaining in the deeper bands would total 1,016–1,059, barely below the zone-wide total (1,101 rooms). The point at which the affected room count drops significantly is 5m: the 1,011 rooms at 3m or more fall to 757 at 5m or more. Inside the zone in Shirahama Onsen, designs that provide evacuation space on upper floors are more likely to be the central issue than approaches that avoid inundation by raising the building.

On the Map — Inundation Zones, Lodging and Designated Tsunami Evacuation Sites

The map below divides the tsunami inundation projection into a roughly 100m mesh and shades each cell by the depth band at its center point (darker means deeper). White circles are the sampled lodging properties (circle size reflects room count), and gray diamonds are the sites Shirahama Town has published as designated emergency evacuation sites for tsunamis. The inundation zone extends continuously across the flatland from behind Shirarahama to Tsunashirazu Bay, while it barely touches the coastal terraces on the Yuzaki–Senjojiki side or the hills of Katata. The distribution of lodging follows this topography, with small and mid-sized properties packed into the commercial district behind Shirarahama.

Of the 60 designated tsunami evacuation sites within the 3km radius, 54 are on high ground, school grounds or temple and shrine precincts outside the inundation zone. The remaining 6 are inside the zone, and 4 of these are buildings in the 5m-plus band — designations that can be read as premised on evacuation to upper floors (vertical evacuation). Several of the designated sites carry the names of lodging properties, showing that hotel buildings play a role in the local evacuation system.

Differences by Size — 47.5% of In-Zone Rooms Are at Four Properties With 100+ Rooms

Broken down by room count, the composition differs inside and outside the zone. Large properties with 100 or more rooms number 4 (523 rooms) inside the zone and 6 (866 rooms) outside. These 4 properties account for 47.5% of the 1,101 rooms inside the zone, meaning about half of in-zone rooms are concentrated at large properties. Mid-sized properties with 30–99 rooms are few inside the zone (2 properties, 125 rooms) and more common outside (11 properties, 644 rooms). Among small-to-mid properties with 10–29 rooms, the split is roughly even, with 20 properties and 329 rooms inside versus 16 properties and 306 rooms outside. Small lodgings with 1–9 rooms (minshuku, vacation rentals, guesthouses, etc.) number 31 properties with 124 rooms inside the zone and 42 properties with 123 rooms outside.

These differences also matter for evacuation planning. Large properties are generally mid- to high-rise reinforced concrete buildings and can more readily offer evacuation to upper floors within the building. Small lodgings with 1–9 rooms and whole-house rentals, on the other hand, tend to be low-rise, so their plans are more likely to assume moving to designated evacuation sites on high ground (horizontal evacuation). The 31 small lodgings inside the zone make up more than half of all in-zone properties by count, so soft measures such as guiding guests along evacuation routes and providing information in multiple languages offer substantial room for small lodgings to strengthen their reliability.

Crossing depth band with property size makes the in-zone composition even clearer. Of the 4 large in-zone properties with 100+ rooms, 3 (423 rooms) lie in the 5m-plus band, accounting for 55.9% of the 757 rooms in that band. Meanwhile, no property with 30 or more rooms falls in the shallow bands under 3m; all 9 properties there have 29 rooms or fewer. Of the 31 small in-zone lodgings with 1–9 rooms, 14 are in the 5m-plus band, and for buildings without upper floors, horizontal evacuation to high ground is the default. Depending on the combination of size and depth, the measures available vary widely even among properties that are all “inside the zone.”

By property type, 21 of the 36 ryokan (720 of 1,352 rooms, or 53.3%) are inside the zone, making ryokan the type with the most in-zone rooms. Only 4 of the 16 resort hotels (138 of 895 rooms, 15.4%) are inside the zone, as many sit on the terraces. Of the 15 minshuku (134 rooms), 10 properties with 78 rooms are inside the zone, suggesting many remain in the traditional lodging quarter behind Shirarahama.

Relationship With Rates — Median Estimated Settled ADR of ¥19,200 Outside the Zone

Next, we examine the relationship between inundation exposure and room rates. We took the 50 properties (31 ryokan, 16 resort hotels, 3 business hotels) for which an estimated settled ADR was available for at least 6 of the 12 months from September 2025 to August 2026, calculated each property’s period average, and compared the medians by depth band. The median for the 25 properties outside the zone was ¥19,200 versus ¥10,700 for the 25 inside, putting outside-zone properties at roughly 1.8 times the level. Within the zone, the median was ¥9,100 for under 3m (4 properties), ¥10,700 for 3m to under 5m (7 properties) and ¥12,200 for 5m and above (14 properties) — all below the outside-zone figure.

Comparing ryokan only, to remove differences in property-type mix, the median is ¥21,400 for the 13 outside the zone versus ¥11,200 for the 18 inside. Room-weighted averages point the same way, at ¥19,800 outside and ¥15,500 inside. The terraces from Yuzaki to Senjojiki host many high-end ryokan and resorts with rooms and open-air baths overlooking the Pacific, and the added value of these views appears to be reflected in their rates. Properties inside the inundation zone are close to Shirarahama Beach and the center of the onsen town, offering convenient beach access and walkability at affordable price points — they can be seen as supporting the depth of Shirahama Onsen’s price range.

The estimated settled ADR for Shirahama Town as a whole averaged ¥14,800 over the 12 months from September 2025 to August 2026. On a monthly basis, the low was ¥11,800 in June 2026 and the high ¥17,400 in December 2025. The January–August 2026 average was ¥14,600, up 6.9% from the same period a year earlier (¥13,600), indicating an upward trend. By month, January 2026 rose sharply at +23.2% YoY, while June was -7.7% YoY and August -1.9% YoY. The seasonality of higher rates during the summer holidays and the year-end/New Year period is clear, reflecting the demand structure of a beach resort.

To compare area-level rates with the surrounding region, we lined up the estimated settled ADR for southern Kii coastal municipalities and Wakayama Prefecture as a whole over the same period. Shirahama Town’s 12-month average of ¥14,800 is the highest among municipalities with 15 or more properties in scope, above Nachikatsuura Town (¥12,900) and Tanabe City (¥12,000), and about 1.5 times the prefectural figure (¥9,700). Its January–August 2026 YoY change of +6.9% also outpaced the prefecture (+2.6%). All of these are coastal municipalities that include tsunami inundation zones, and in Shirahama, inundation exposure does not show up as a drag on area-wide rates. The rate gap between inside and outside the zone is more naturally read as reflecting differences in location within the town (the flatland behind Shirarahama versus the terraces).

Supply Trends — More Than 80% of Rooms Added Since 2017 Are Outside the Zone

Based on opening and closing dates in the property master, the number of properties and rooms within the 3km radius grew from 97 properties and 2,531 rooms in 2012 to 190 properties and 4,156 rooms in 2026. Rooms increased by about 1,100 in 2017–2019 in particular, reflecting a run of large property openings during that period. Since 2020, the room count has been roughly flat, and growth in the number of properties has been driven mainly by small properties such as vacation rentals and guesthouses.

Splitting the 132 sampled properties by opening period, of the 56 properties and 930 rooms opened since 2017, only 23 properties and 170 rooms (18.3% of rooms) are inside the zone. For the 58 properties and 2,044 rooms opened in 2016 or earlier, 29 properties and 907 rooms (44.4%) are inside the zone, showing a clear tendency for newer supply to locate outside it. By property count, there have also been 23 new openings inside the zone, but many of these are whole-house rentals and small lodgings; the large blocks of rooms have gone to the terraces and hills. This can be read as site selection being reflected to some degree in development decisions since the tsunami inundation projections were published.

Zoning and Land Prices — 65% of Properties in Commercial Zones Are Inside the Inundation Zone; Commercial Land Prices Flat

We also checked the overlap with zoning. Commercial zones with a 400% floor area ratio host 46 sampled properties with 1,238 rooms, of which 30 properties and 526 rooms are inside the inundation zone (65.2% by property count). The commercial zone is designated over the center of the onsen town behind Shirarahama; while its high floor area ratio leaves room for redevelopment, sites there tend to overlap the inundation zone. Category II residential zones (200% FAR) contain 30 properties with 1,185 rooms, 13 properties and 477 rooms of which are inside the zone. Many large properties are spread across residential and commercial zones.

For land prices, we tracked five official land price and prefectural land price survey points within the radius since 2019. The two commercial points at the center of the onsen town (Shirahama Aza Kamibori, prefectural land price survey; Shirahama Aza Hamadori, official land price) both lie in the 3m-to-under-5m inundation band, at ¥76,200 and ¥64,100 per ㎡ in 2026. Declines since 2019 were limited to 1.5–3.3%, and prices have been flat to slightly rising since 2023. The three residential points outside the zone range from ¥30,700 to ¥38,600, also showing only small movements. That commercial land prices inside the inundation zone have not collapsed indicates that the market continues to recognize the locational value of the onsen town center.

Supplementary Indicator — 24 Properties and 355 Rooms in Sediment Disaster Warning Zones

Because Shirahama Onsen’s coastal terraces and hills run close to the sea, we also checked sediment disaster warning zones separately from tsunami exposure. Of the 132 sampled properties, 24 properties with 355 rooms are located in sediment disaster warning zones (some in special warning zones), and 12 properties with 133 rooms of these also overlap the tsunami inundation zone. For sites near the edges of terraces or slopes, the high ground that serves as a tsunami evacuation destination and the management of sloped land become linked issues. In investment decisions, it is useful to check both hazards — tsunami and sediment disasters — on the same map, and to compare multiple hazards alongside rates and disaster-prevention investment at the trade-area level.

Implications for Investment — Design, Insurance and BCP Issues That Change by Depth Band

Based on the tallies so far, lodging assets in Shirahama Onsen can be organized into three broad zones. The following summarizes, for each combination of depth band and location, the issues worth considering when rebuilding, renovating or acquiring.

The timing of a rebuild or major renovation is the most effective opportunity to build these issues into the business plan. Large properties in the 3m-plus band in particular also hold value as local disaster-prevention infrastructure, since their upper floors can serve as evacuation space for guests and nearby residents. Indeed, within the radius there are cases where hotel buildings have been designated as tsunami emergency evacuation sites. Because insurance premiums and the scope of coverage vary widely with a building’s structure, age and location, it is useful in acquisition due diligence to share the inundation depth band as a precondition with insurers and designers at an early stage.

Summary

In the Shirahama Onsen area, 57 properties with 1,101 rooms (36.2%) of the 132 properties and 3,040 rooms confirmed on sale lie inside the tsunami inundation zone designated by Wakayama Prefecture, most of them in bands with a projected depth of 3m or more. About half of in-zone rooms are concentrated at four large properties with 100+ rooms, while by property count, small lodgings with 1–9 rooms predominate. On rates, the median estimated settled ADR of properties outside the zone (¥19,200) exceeds that of properties inside (¥10,700), and higher-priced properties are concentrated on the coastal terraces. More than 80% of rooms added since 2017 have chosen sites outside the zone, signaling a shift in where new supply locates.

The locational value of Shirarahama Beach and the onsen town center is also reflected in land prices, with commercial land prices inside the zone holding flat. To make the most of this locational value over the long term, the key is to structure design, equipment placement, insurance and BCP around the inundation depth band at the rebuilding or acquisition stage. The inundation projection is an official maximum-class scenario, and we hope readers will use the tallies in this article as material for understanding the characteristics of each location.