Both sedges (Carex species) and pampas grass (Cortaderia selloana) have sharp edges that can cut. Pampas grass is well known for that and most carex stay smaller than 4' so I'd go with a dwarf pampas, most likely.

Hi there,
I think it is some segde/ Carex. There are at least 2 or 3 European species that grow in wet spots. (I did and gave some botany lessons at university in Germany, on native flora and grasses)
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ID-Help for Carex: if you cut off a single bundle-like shoot, it should be triangular in shape. And the grass blades show a M-like shape, well slightly flattend, if you cut it in halves and look at the cross section.
And the sharp edges are typical as well.
Perhaps you can google Carex acutiformis, C. acuta, C. elata and see if the pictures ring a bell.
And I think you can cross Cortaderia from the list as it does badly with moisture in winter.
Perhaps that helps, bye Lin