The Ostoja Zachodniowołyńska Dolina Bugu site PLH060035, with an area of 1556.1 ha, was established mainly to protect a fragment of the Bug River valley with its oxbows, humid meadows and riparian forests. In a stretch of the valley between the villages of Czumów and Gródek, the steep loess slopes are inhabited by thermophilous plants. These slopes lie in the Hrubieszów Basin (Zachodniowołyńska Upland) in Hrubieszów Township (Hrubieszów County). Several of the most valuable fragments were put under protection in 1960 in the form of a natural monument as a 0.27 ha stand of xerothermic vegetation, and then in the 1990s in the form of the "Błonia Nadbużańskie" environmental use area. A plan to create a reserve on the site of the environmental use area was unsuccessful.

The loess slopes of the Bug River valley are places where floristic xerothermic grasslands (Code 6210) occur. Thirteen plant species under protective status have been noted here. Among the most valuable is Chamaecytisus albus, listed in the Polish Red Data Book of Plants. This is the only known site of this species in the country. Additionally, other protected species found here are: Gypsophila paniculata, Prunus fruticosa, Scorzonera purpurea, Primula veris and others. Other plant species present here but lacking legal protection include: Peucedanum alsaticum, Libanotis pyrenaica and Salvia nemorosa. The greatest feature of interest in the fauna of "Błonia Nadbużańskie" is Spermophilus suslicus, still living here in scattered colonies among the arable land. It formerly inhabited the extensive pastures in the river valley, but the Bug River's spring flooding destroyed much of the population. Noteworthy among the invertebrate fauna is the colorful representative of the moth family seen in this area - Pericallia matronula - listed in the Polish Red Data Book of Invertebrates. Of historical interest is the early Middle Ages settlement of Gródek, overgrown today with xerothermic vegetation.

The Bug valley slopes were used as pastures just half a century ago. Today they are not used for grazing and the grasslands are occasionally burned. Spillage of herbicides from cultivated fields located at the crests of the slopes related to excessive development and the lack of grazing have resulted in the growth of overly dense ground cover and layers of thatch - also known as "steppe felt". This makes it difficult or even impossible for seeds of the xerothermic plants growing here to sprout.