"a large floating population" is a correct and usable phrase in written English.
You could use it to refer to a group of people who are not permanently living in one place, such as refugees or nomads. For example, "The country is facing a challenge of managing a large floating population of refugees."
In addition to the city's population, there is frequently a large floating population of pilgrims, who sometimes bring the bodies of the deceased for interment or come with elderly and infirm family members who wish to live their last days in the holy city before being buried there.
The hospital has 100 beds and assists a large floating population including 10 000 hospitalisations, 57 000 emergencies and 152 892 laboratory requests (12 206 from the inpatient ward) annually.
Many also sleep on these streets, or in tiny rooms in backyards: temporary lodging for this large, floating population.
The land use/cover change reveals the large floating population in Lhasa and underscores the role of high population growth in the economic prosperity of the former agricultural and pastoral areas in the city.
HDL1 is a large floating particle which plays an important role in reverse cholesterol transport.
The large "floating populations" of migrant workers make conducting censuses in urban areas difficult; the figures below include only long-term residents.
The formation of the Liaohe River hotspot can be attributed to the post-reform development of downstream Liaohe River Plain and large cities including Shenyang, which, with a large demand for labor, attracted a floating population of many ethnic minorities from the surrounding areas.
We conclude that people adapted their routines to play the game, concentrating geographically in places with a high floating population.
Both Beijing and Guangdong are economically developed and have large proportions of floating population [ 18, 19].
There is also a floating population that sleeps overnight in the country's many 24-hour Internet cafes and saunas.
Furthermore, it is a floating population that comes and goes because distances are so short.
