Where does Kite Beach's sand come from?

Probably mainly from western Cabarete Bay: the waves push sand north-west along the shore, past the rocky Kite point, towards Kite Beach in every month's average. That is the waves' capacity, not a measured movement. The small beach on the Cabarete side of the Kite point fills in summer and empties by April, opposite to Kite Beach, but how sand passes the point is not settled. The small waves push sand along the beach face towards Kite Beach, while the current a little further out, in both current models, runs past the point into Cabarete Bay. Locals report a sandy bottom there, so the current has sand to carry and some sand probably goes that way too. Which moves more sand depends on how coarse the sand is and how much of it the waves stir up, and neither has been measured.

Why is Kite Beach narrower in summer?

Ten years of satellite images show Kite Beach is widest in February and narrowest in September, about 18 m apart in the typical year (14–19 m depending on how the waterline is traced). The likely reason is the waves' push along the shore, and the wave models show it switching with the seasons. The trade winds blow from about the east in every month's average; what changes is the swell. From about September to April, north-east swells push sand into Kite Beach from both ends; from about June to August, short easterly trade-wind waves reverse the push at the beach's north-west end and drain that end north-west. This is the waves' capacity to move sand, not measured movement. The models get the timing but not yet the size of Kite Beach's swing; the summer stretch's width they do reproduce. On windy summer afternoons the wind also blows some dry sand along the beach and inland, which may add a little to the summer loss.

Is there a channel through the reef at Kite Beach?

Yes. Local photos and the satellite record of breaking waves show a gap in the reef off the north-west half of Kite Beach. Water pushed over the reef by breaking waves flows north-west along the back-reef and returns to sea through this channel and, in larger amounts, through the lower broken reef at the north-west end of Kite Beach. In the XBeach model the channel is a surging rip, strongest in big north swells (about 1 m/s on average, surges up to about 1.9 m/s) and weaker on typical winter days and in big north-east swells (about 0.35–0.5 m/s on average). XBeach also confirms the lower reef at the north-west end as the main exit. The channel's depth has not been measured, so these speeds are estimates.

Does Encuentro get its sand from Kite Beach?

Probably little. The waves could push a lot of sand towards Encuentro, yet Encuentro is not growing: its width shows no clear trend over ten years and swings only a few metres with the seasons. Either little loose sand reaches it, or sand passes through towards Sosúa or offshore as fast as it arrives; the satellites cannot tell which. Locals report plenty of sand on the bottom all the way to Encuentro and out past the reefs, so sand passing through is the more likely, though Kite Beach may still hold back some of the sand moving along the beach face.

Does north swell change the sand drift at Cabarete?

Only locally. True north swell comes on about one day in thirty, mostly from November to April. On those days the waves push sand south-east at the south-east end of Kite Beach, but on the Cabarete side of the Kite point and in western Cabarete Bay the push still runs towards Kite Beach. (This is the waves' push along the beach; the current near the point runs towards Cabarete Bay in both seasons.) The satellites show the effect: within a few days of a typical north swell the south-east half of Kite Beach is about 2 m wider and western Cabarete Bay about 1.7 m wider, so some sand passes the point into the bay.

Where does Kite Beach's sand go?

A computer model of the water, waves, wind and sand along the reef at Cabarete, from Encuentro to Cabarete Bay. Slide through the year to see how the beaches change with the seasons, or pick a storm to see where the water goes. Click on the water to drop a handful of floats and watch where the current takes them.

Read the short summary or the full report, with all the figures and methods.

Water currents (moving lines) Wave height Depth Sand drift along the beach Beach wider / narrower than average Reef (shallower than 2 m) Place names

Loading the model…

The year at a glance

How much wider (above the line) or narrower (below) each beach is than its average, from ten years of satellite pictures; and the average wave height offshore. The dashed line marks the month on the map.

Which program tells us what

No single program can do everything, so the study chains several together. Each answers a different part of the question, and the satellites check the answers against what the beaches actually did.

ERA5: offshore waves and wind→SWAN: waves over the reef→Current model: water flow→Sand formula: sand carried |XBeach: surges, beach cut and fill|Sentinel-2: what really happened

Program or data	What it is	What it tells us	Where you see it here
Sentinel-2 satellites	European satellites that photograph the coast every few days: about 340 clear pictures from 2017–2026, corrected for the tide. The traced line sits in the wet sand, so it shows changes in beach width well; the timing of the seasons is firm, the sizes uncertain by several metres.	What the beaches actually did: how wide each one is month by month, and how that changed over ten years. Also where waves break, which reveals the reef gaps, and where the water turns cloudy after big swells.	Green and red dots (beach wider or narrower); the chart "The year at a glance"; the position of the Kite Beach channel.
ERA5	A global weather record from the European weather centre (ECMWF): offshore waves and wind every hour since 2017.	What the ocean and the wind were doing offshore, before the reef changes anything.	The waves and wind dials; the monthly summaries; the weather behind every model run.
Puerto Plata tide gauge	The nearest measured tide.	The water level for each satellite picture and each model run, and the high- and low-tide cases.	The tide in the storm cases; the tide correction behind the beach dots.
Allen Coral Atlas, drone surveys and local photos	Depths and reef types estimated from satellite images (typically to within 1–3 m), checked against drone surveys, local photos and local knowledge ("knee deep", "over head high").	The shape of the seabed that everything else runs on: where the reef is, how shallow it is, and where the gaps are. The channel's depth is still a guess.	The depth colours; the black reef outline; the red dashed channel.
SWAN	A standard wave model, run thousands of times for every combination of swell size, period, direction and tide.	How the offshore swell changes as it crosses the reef: where it breaks, how big it is at the beach, and which way it pushes sand along the shore.	The wave-height colours; the orange sand-drift arrows (year view).
Current model	A shallow-water flow model run on the computer's graphics card, driven by the breaking waves from SWAN, the wind and the tide.	Where the water pushed over the reef goes: along the back-reef and out through which gaps, and how fast, averaged over an hour and a half.	The moving white lines; the red and blue in/out dots; your floats.
Sand formula (Soulsby–van Rijn)	A standard formula for how much sand a current can carry when waves stir up the bottom.	How much sand the currents could carry. It is not calibrated here and the grain size is assumed, so read it for direction and pattern, not amounts.	The orange arrows in the back-reef (storm view).
XBeach	A model built for surf zones. It follows the sets of waves, the surges they drive (surf beat), and how the beach and seabed change.	How big swells cut the beach and park the sand just offshore, and how hard the water rips out through the channel in surges: strongest in a big north swell, about 1 m/s on average and up to about 1.9 m/s, and weaker on other days. Its currents agree with the current model at the Kite point and broadly along the coast, and it confirms the main exit at Kite Beach's north-west end. One short test of a whole year with it failed (a start-up effect of the model); that does not affect the seasonal switch the wave models show. Its year-round sand budget over the whole reef did not match the satellites, so it is not used for amounts.	The storm summaries, the channel speeds and the report.
SWASH	A wave-by-wave model along single lines from the reef to the beach.	That surf beat is usually a bigger water motion at the beach than the ordinary waves that get through the reef.	The "surf beat" explanation below.
Wind-blown sand formula (Kawamura)	A standard formula for dry sand blown by the wind, using ERA5 wind and rain.	How much dry sand the wind blows along the beach and inland, mostly on windy summer afternoons.	The monthly summary ("the wind blows dry sand off Kite Beach this month").

What you are looking at

The reef and the back-reef: A coral reef runs along the coast a few hundred metres out. The shallow water between the reef and the beach is the back-reef. Waves break on the reef and push water over it into the back-reef. That water has to get back out to sea, and it does so as currents through the lower and deeper gaps in the reef.
Water currents: The moving white lines follow the average current. Brighter and longer lines mean faster water. In the year view, each month's currents mix all seven model cases (typical winter and summer days, trade winds, big north-east and north swells at different tides), weighted by how often those conditions happened that month in 2017–2026.
The two exits behind Kite Beach: The back-reef water splits behind Kite Beach (the "water splits here" label), like rain off a ridge: at about 5.2 km, roughly 350 m before the Kite point, on typical winter days and in big north-east swells, and at the point itself (5.6–5.7 km) on summer and trade-wind days. North-west of the split the water runs north-west along the back-reef; south-east of it, it drains into Cabarete Bay. The main exit through the reef at Kite Beach is the lower, broken reef at its north-west end and along the between stretch: about 270–420 m³/s goes out there in the current model, and XBeach confirms it as the main exit. More water still leaves across the open middle of Cabarete Bay, where there is no reef. The second exit is the channel off Kite Beach that surfers and kiters know. Its position comes from local photos and from the gap in the breaking waves in ten years of satellite pictures. XBeach shows it as a surging rip: as each set of waves pushes water over the reef, it surges out through the channel, at about 1 m/s on average and up to about 1.9 m/s in a big north swell, and more gently (about 0.35–0.5 m/s on average) on typical winter days and in big north-east swells. Neither exit's depth has been measured.
Sand drift along the beach: The orange arrows show which way the waves push sand along the shore that month, and how hard (longer = stronger). That is how much sand the waves could move; how much actually moves depends on how coarse the sand is and how much of it the waves stir up, neither of which has been measured.
Beach wider or narrower: Green dots: the beach is wider than its yearly average that month; red: narrower. From ten years of Sentinel-2 satellite pictures, corrected for the tide, as a smooth fit to the typical year.
Surf beat: The slow surge of water up and down the beach every minute or two, driven by sets of bigger waves breaking on the reef. It pushes water out through the gaps in bursts much stronger than the averages shown here.

The story in short

The waves' push meets at Kite Beach. In every month's average the waves push sand into Kite Beach from western Cabarete Bay, past the rocky Kite point. From about September to April they also push it in from the north-west; in summer the push at the beach's north-west end reverses and drains that end north-west. That is the waves' capacity, not measured movement; the satellites show Kite Beach swinging with the seasons but not steadily growing over ten years.
The small beach by the point is a seasonal store. It fills in summer and empties by April, opposite to Kite Beach, and it has narrowed by about 2 m a year. How sand moves between the two is not settled (see the Kite point, below).
Encuentro changes little. West of Kite Beach the waves could carry a lot of sand towards Encuentro, yet its width shows no clear trend and only a small seasonal swing: either little loose sand arrives, or it passes through. Locals report plenty of sand on the bottom, so passing through is the more likely.
Big swells cut the upper beach and park the sand just offshore in the models, except at the sheltered middle of Kite Beach, where the change is tiny; calmer weather brings it back. The satellites show no clear mark after big swells in general, but north swells widen the south-east half of Kite Beach by about 2 m each, within a few days.
The wind blows dry sand along the beaches and inland, mostly on windy summer afternoons. The sand blown inland usually does not come back: a small, slow loss, probably a few cubic metres per metre of beach a year.
The water behind the reef splits behind Kite Beach. North-west of the split it runs north-west and turns out to sea at Kite Beach's north-west end, a possible route for sand to leave. The Kite Beach channel is a surging rip, strongest in big north swells.
At the Kite point the models agree. The current model and XBeach both drain the water near the point into Cabarete Bay, and the wave directions in the models and the satellite images agree. Which way the sand goes there is still unknown: the small waves push sand along the beach face towards Kite Beach, while the current a little further out runs towards the bay. Locals report a sandy bottom there, so the current has sand to carry and some sand moving south-east past the point is likely; which wins depends on how coarse the sand is and how much of it moves. Nothing has been measured there yet.
Mostly back and forth. Kite Beach swings by about 18 m with the seasons, and some beaches by up to about 26 m; over ten years most show no clear trend, except the small beach by the point (narrowing) and the stretch north-west of Kite Beach (widening). Sand passing straight through, towards Sosúa or out to sea, would not show in the beach widths, and the models cannot yet measure it.
After big winter swells the water outside the reef is cloudier all along the coast, most of all off Cabarete Bay (satellites). That fits plenty of sand on the bottom being stirred up, as locals see in the murky water. Rain runoff, which often comes with the same swells, has not been separated.

Sources and methods

Beaches: Sentinel-2 satellite images 2017–2026 (Copernicus, via Earth Search). Depths: the Allen Coral Atlas (drone surveys used as a check), with the reef crest kept shallow and the Kite Beach channel added from local photos. Tide: the Puerto Plata tide gauge (UHSLC). Waves and wind: ERA5 (ECMWF). Models: SWAN (waves), a shallow-water current model on a graphics card (currents), XBeach (surf beat and beach change), SWASH (wave by wave across the reef), a sand-transport formula (Soulsby–van Rijn) and a wind-blown sand formula (Kawamura). Map tiles: Esri, Maxar, Earthstar Geographics.