The alarming state of Rio de Janeiro’s iconic sandy expanses has all but dominated the news cycle of late when it comes to horrifically polluted beaches.

This week, however, that unsavory spotlight has shifted (but not completely) to Hong Kong, where a majority of local beaches have been overwhelmed by a veritable tsunami of plastic waste and assorted household trash.

It would be a stretch to label the beaches in question, including the usually bustling Cheung Sha Beach on Lantau Island and Stanley Beach on Hong Kong Island, as spotless and exceptional pristine. Not-keen-on-recycling Hong Kong has long suffered from a significant waste problem that extends to its beaches and coastlines. In fact, more than 15,000 metric tons of marine debris plucked from coastal areas each year according to Coastal Watch estimates.

Litter-strewn beaches are the norm.

Yet the sheer magnitude of this summer's foul mess — a “plastic tide” per Hong Kong's English language newspaper, the South China Morning Press or SCMP — has caught local conservation organizations off-guard. It’s safe to say the size and scope of this monstrous rubbish-wave has never been seen before in Hong Kong.

Cheung Sha Beach, Lantau, Hong KongA day at the beach on Lantau Island, Hong Kong. (Photo: Ocean Recovery Alliance/Facebook)

An estimated six to 10 times the normal volume of what normally washes ashore on Hong Kong beaches, according to the Environmental Protection Department, and the unsightly onslaught has left volunteer cleanup groups overwhelmed yet determined to keep at it. It’s left everyone involved, concerned citizens included, perplexed as to how such a massive amount of waste could enter the ocean and where it originated.

It’s somewhat of a mystery, really, although it’s become increasingly clear in recent days that this isn’t a homegrown problem.

Referring to the amount of waste as “unprecedented,” Gary Stokes, Southeast Asia director of Sea Shepherd Conservation Society, tells CNN: “Trash on the beach is nothing new in Hong Kong, but this is completely different to what we would normally see.”

While an exact source of the waste may not yet be pinpointed (and one wonders if it ever will be), both governmental officials and environmental groups have ID’d a culprit: mainland China. After all, the proof is printed directly on the labels and packaging of the offending rubbish.

Stokes notes that most rubbish that washes ashore on Hong Kong’s beaches originated within the autonomous territory of over 7 million residents. Mainland-produced trash swamping Hong Kong's beaches, especially in such a staggering amount, is a rarity.

Beach on Lantau Island, Hong Kong This normally inviting stretch of sand on Hong Kong's Lantau Island looks like nice place to to take a leisurely stroll, right? (Photo: Daniela Ritrovato/flickr)

Cheung Sha Beach, Lantau, Hong Kong Eh, not so much over the past two weeks. (Photo: Ocean Recovery Alliance/Facebook)

So why? And why now?

In a statement issued to the SCMP, the Environmental Protection Department claims that an unfortunate intersection of human activity (illegal dumping) and Mother Nature (historic rainfall and subsequent flooding on the Chinese mainland) is largely to blame:

We suspect that the floods in mid-June on the mainland might have brought the refuse to the sea and then the refuse is brought to Hong Kong by the southwest monsoon wind and the sea currents.

A similar phenomenon happened in 2005 when a massive amount of debris and refuse was found at various beaches and coastal areas of Hong Kong after a serious one-in-a-100-year flood on the mainland.

Additionally, it’s believed by environmental groups that some of the marine waste landing on Hong Kong’s beaches originated from an illegal garbage dump located on Wai Lingding Island, which is located just 7 nautical miles south of Hong Kong Island in the mainland-governed waters of the Zhuhai municipality.

“It's pretty much like a glacier of trash that keeps sliding down the hill,” Stokes tells CNN of the illicit oceanfront dump.

“The make-up of the trash is also alarming — there are so many clear plastic cups and bowls of exactly the same type, which would indicate it’s coming from one location,” Stokes explains to the SCMP noting that this is the first time Hong Kong has stepped up and, for the first time, accused China of polluting its coastline. “These aren’t from accidental run-off into the sea from random sources — this looks like illegal dumping.”

Hong Kong pointing a direct finger at mainland China is an impressive first step, but the government has yet to announce any sort of plan of attack when it comes to cleaning up the unholy mess — or taking steps to prevent such an influx from happening again.

And so, Hong Kong residents, many of whom frequent the safe-to-swim-at beaches that have been rendered absolutely disgusting in recent days, have taken it upon themselves to clean up miles upon miles of trash-strewn sand in the absence of governmental assistance or intervention.

As Lisa Christensen of Hong Kong Cleanup Challenge explains to the SCMP: "Volunteer cleanups are an educational tool and a source of data. They are not the solution to the tidal wave of trash in Hong Kong’s waters."

Matt Hickman ( @mattyhick ) writes about design, architecture and the intersection between the natural world and the built environment.