A stackable barrier unit includes: an elongate main body having a top surface, a bottom surface, longitudinal ends, and two sidewalls each having an upper margin joined to the top surface a lower margin extending tower than the bottom surface of the main body. A base width defined between lower outer margins of the sidewalls is greater than a top width of the top surface. Engagement extensions having engagement features extend from the longitudinal ends for linking two or more barrier units together. The engagement features may include a tapered pin and a hole. A rib may connect the first sidewall to the second sidewall below the bottom surface. A channel may be formed in the top surface of the main body directly above and parallel to the at least one rib.