Not European but I'll take a guess. Hope this helps:

In the UK (and maybe elsewhere in Europe) a "garden" is what people in the US would call a "yard"; an open space near a residence. Often, but not necessarily covered in grass or plants.

"Garden paving" would mean covering it with something impervious to rain, such as concrete or asphalt.

So a "garden pavement tax" would be a penalty for people who choose to cover up soil with an rain-blocking material, to encourage them to use an alternative which allows the ground to soak up the rain.

As an example, in my town there is a public park in a flood plain, its driveways are made with "permeable pavers"[1] which are basically thick brick tiles with holes in them. They allow the rain to go through to the ground instead of building up and flooding the parking lot.

[1]: https://duckduckgo.com/?q=permeable+paver&iax=1&ia=images

We have similar drainage fees here in Houston, based on the amount of impervious ground cover on the property. We've had a lot of flash flooding in the past 20 years because of the growth of neighborhoods and commercial properties with large parking lots on what used to be prairies on the perimeter of town. New commercial construction typically has to have catchment basins, permeable concrete, or other runoff mitigation strategies. There is, however, a lot of legacy properties which don't handle their runoff, and an outdated storm sewer system, so we still have problems.

Because of urbanization, the paving of gardens, the water does not sink into the ground over large areas. The sewage systems are having difficulty coping with this. Because of this they're thinking about taxing the paving of gardens.

There's a municipality planning to do this starting January 2018.

https://www.gemeente.nu/ruimte-milieu/minder-groen-tuin-bete...

Tangential, but:

I'm wondering what the ratio of tiled-over private gardens is to tiled-over public spaces (sidewalks, streets, etc.) which are omnipresent in the NL. I'd guess that the poor drainage relating to the public spaces is much greater than the poor drainage due to private tiled gardens.

I don't know about the Netherlands specifically, but in general the amount of land area devoted to public spaces is very small, albeit intensely developed, compared to residential land, which is vast and less intensely developed.

I think residences in the US and residences in Europe are quite different, and especially the Netherlands are quite densely populated. I would say that the area that's used in the US to have a driveway would work quite well in the Netherlands to have a big garden (yard).

Yeah it is quite different in the NL. Private space is much more limited compared to public space. Cities are dense, peoples' private gardens are small if they exist at all, public spaces are abundant. This isn't the land of sprawling residential space.

Sure, but streets need to be paved. Backyards not so much.

I think pasta is talking about this:

https://radar.avrotros.nl/nieuws/detail/belastingvoordeel-vo...

Translated:

People who replace their garden tiles with grass, have to get a tax premium.

That's what Lambert Verheijen of the water board "Aa and Maas" is pleading for. This was reported thursday by BNR. Because there is too much paving, the water doesn't sink into the ground well enough and the risk on flooding increases. Verheijen got inspiration in Germany, where a comparable premium is already in place.

Sounds like a disincentive for paving with impenetrable ground cover. Rainfall is not absorbed when the ground is paved. Instead, it collects and increases flash flood risk. To compensate for this, the rainfall collection and pumping infrastructure must be more robust. Perhaps this tax will be spent on such improvements?

Here's an English article.

http://www.dutchnews.nl/news/archives/2017/07/brabant-villag...

The more you seal off your land with buildings, or pavement, or even patio tiles, the more the rain will wash off your land and flood people who live downhill from you. So the Dutch pay closer attention to the issue than other nations.

Don't forget the sewers.