Herbert Hoover National Historic Site protects sensitive tallgrass prairie and is directly adjacent to a major highway in eastern Iowa. Transportation noise from the highway spreads across most of the park and is a concern for wildlife. Recent efforts to excavate a water detention basin in the park resulted in a significant amount of excess dirt, dirt that the park wanted to use to build a noise berm. To determine how best to construct the berm to reduce highway noise and improve communication conditions for wildlife, different berm configurations were modeled using sound propagation software (CadnaA). We found that installation of a noise berm along Interstate 80 would reduce highway noise entering the park by 1 to 20 dB LAeq, 24hr (12.5Hz - 20kHz) re 20 µPa. Based on the noise model results, the park decided to install two berms. Along with a collaborative team, the park designed the berm shape and location to reduce highway noise, preserve the cultural landscape, and minimize the need for post-construction prairie restoration. The berm is slated to be installed in 2020. To determine if the predicted noise reduction improves wildlife habitat, field measurements of highway noise and bioacoustic activity before and after berm construction will be collected. A comparison of pre and post measurements, summer 2019 and 2021 respectively, will determine how effective the noise berms are at reducing highway noise levels and if wildlife responds to the change. Given that transportation noise is known to reduce effectiveness of communication for a variety of wildlife species, we hypothesize that the reduction in noise will result in improved communication conditions for wildlife and therefore, bioacoustic activity will increase after the berm is installed.
Partnerships and Collaborative Approaches for Improving Transportation Ecology