Semínský přesyp NNM was declared in 1980 on an area of 0.55ha at an elevation of 200 metres above sea level and lies in the village of Semín and near the town of Přelouč in the Pardubický kraj (Pardubice Region). The monument includes two separate areas with the remnants of inland sand dunes – on the village green and to the north of the former brewery.
Geologically these two small territories are indistinctive bodies of airblown sands of late Pleistocene to Holocene age, which have been partially quarried. The sand grains have an average diameter of 0.5mm.
The main subject of the protection is the milk-vetch Astragalus arenarius, which grows on the fringes of the unstable sands. This species is found nowhere else in the Pardubice region. The plant communities belong to the Corynephorion canascentis alliance. Other characteristic psammophilous (sand-loving) plants which grow here include the chamomile Anthemis ruthenarium, grey hair-grass (Corynephorus canescens) and Morison’s spurrey (Spergula morisonii).
Insects which can be found here include the burnets Zygaena viciae and Zygaena angelicae as well as the blue-winged grasshopper (Oedipoda caerulescens).
The grasses in the protected area have to be cut every year and opportunist tree species occasionally need to be cut back. A special management measure involves occasionally breaking up the turf on the fringes of the sand deposits.