Japanese knotweed is easily identifiable by its red stems:
and broad, somewhat shovel-shaped leaves:
Like most invasives, Japanese knotweed was introduced intentionally probably sometime during the 1800s. It has been used ornamentally in the Northeast United States and more recently was used for erosion control in the Northwest United States. Using non-native plants as erosion control in areas where native plants have been wiped out is an ongoing practice. Though I will assume that people making these decisions for the DCR or like organizations have done their research it still seems like a troubling practice with the knowledge of how much invasive plants have changed our local ecosystems.
Japanese knotweed is also edible and contains many valuable nutrients including vitamins A and C, zinc, phosphorus and manganese. It also contains the compound resveratol which is also found in the skin of grapes used to make red wine. This compound is what gives red wine its cholesterol-lowering properties. Research on resveratol is ongoing and many believe that it may be useful in fighting Alzheimer's and possibly even extend life expectancy.
As usual the best thing you can do to help the spread of Japanese knotweed is to try getting rid of it if you see it on your property. Most infestations can be removed manually if one is sure to remove the whole plant and bag and dispose of all parts efficiently. You may also want to encourage your neighbors and local parks managers to be on the lookout for Japanese knotweed because it can recolonize disturbed areas very quickly (are we seeing an invasive plant trend?).