From Airport Cooperative Research Program (ACRP) Report 125, Page 15: The research team has found that more research is needed to accurately quantify bird strike risk. As an industry, there is an accepted understanding that water on an airfield is a hazardous wildlife attractant. Additionally, there is some research that quantifies the parameters of this attractant, but more information is needed. Specifically, the industry would benefit from a greater understanding of stormwater best management practices (BMP) location in relation to the airport movement areas. It would be beneficial to quantify a distance from movement areas where risk of a strike becomes minimal or “acceptable,” within the angle of attack (AOA). Airports rarely have a mechanism for regulating stormwater BMPs off of their properties. Also, it would be beneficial to know the effect on risk when manipulating the placement, not just distance, of stormwater BMPs on or around the AOA. For example, is it more or less risky to construct all ponds on one side of the movement areas, potentially reducing the number of birds crossing over? Or, would it be best to create ponds as far apart from one another as possible to create an isolation affect? These are questions that warrant further investigation, perhaps both on stormwater BMP placement and patterns in wildlife movements. As previously addressed, this ACRP project focuses on the relationship between man-made stormwater BMPs and potentially hazardous water-dependent bird species to decrease the risk of a bird strike. The research needs to be expanded to include all hazardous birds, terrestrial vertebrates (or potentially hazardous wildlife), and more habitat types. More research is needed on the synergistic effects of numerous desirable habitat types located on or around airports. For example, how does placing a stormwater BMP between agricultural fields and an airport affect risk? In regards to quantifying the hazards of all wildlife, there are several published lists containing relative hazard scores for species involved in aircraft strikes. For the purposes of this ACRP project, the research team has utilized the list published by DeVault et al. (2011), which combines mammals and birds, comparing their risks to each other. There are other published rankings, with different relative hazard scores, that separate birds and mammals (Dolbeer et al. 2013). As an industry there is a need for relative hazard scores, which are universally accepted, and clearly defined. The methodologies resulting in the universally accepted scores also must clearly define hazard and risk. Does hazard incorporate both likelihood and severity, or should it be limited to severity only? Should the scores be based solely on wildlife biomass? If so, how do we quantify biomass for small species that commonly flock (e.g., European starlings)? In addition, there appears to be substantial research on the attractiveness of airport turf grasses to wildlife; however, there is a need for more research on the attractiveness of aquatic vegetation to hazardous wildlife. It would be beneficial to airfield managers and planners to have a generic list of aquatic vegetation that is least attractive to these water-dependent species. There is some research on the design parameters of stormwater BMPs that are attractive to wildlife, but some of the language is potentially confounding. For example, AC 150/5200- 33B recommends designing stormwater BMPs with a linear edge to decrease attractiveness, the WashDOT Manual recommends a length-to-width ratio of the BMP of 3:1 or greater to decrease attractiveness (WashDOT 2008), and research from Blackwell et al. (2008) and Fox et al. (2013) suggests that an increased perimeter irregularity (when compared to a perfect circle) leads to an increase in bird attractiveness. These sources are somewhat contradictory by implying a long, narrow, linear BMP is least attractive (WashDOT 2008) and also suggesting a BMP designed like a perfect circle is least attractive (Blackwell et al. 2008; Fox et al. 2013). The research team believes that perhaps one set of design criteria (long and linear) refers to reduced surface area whereas the Blackwell et al. (2008) definition of perimeter irregularity refers to the amount of available shoreline. Both increased surface area and increased shoreline are proven attractive characteristics in BMP design (Fox et al. 2013). However, these parameters need to be further investigated and specific recommendations should be made to determine which design is actually preferable from a wildlife hazard management perspective. Finally, it would be most beneficial to eliminate the attractant all together. More research is needed to either develop alternative methods for mitigating stormwater for water quality purposes, etc., or to reduce the costs of existing systems that completely enclose the stored water. Some airports are converting to stormwater master plans that only include “overland flow” as the method of discharging stormwater, rather 16 than proposing water storage. For example, North Carolina state legislature passed Senate Bill 229 in 2011, amending certain environmental and natural resource laws. Section 6 specifically directs the state Department of Environment and Natural Resources to accept alternative measures of stormwater control at public airports in accordance with AC 150/5200-33B. Per Section 6 of the bill, “the Department shall not require the use of stormwater retention ponds, stormwater detention ponds, or any other stormwater control measure that promotes standing water . . . at public airports . . . [or at any] development projects located within five statute miles from . . . an air operations area. . . .” The guidance continues, “The Department shall deem runways,
taxiways, and any other areas that provide for overland stormwater flow that
promote infiltration and treatment of stormwater into grassed buffers,
shoulders, and grass swales permitted pursuant to the state post-construction
stormwater requirements.” These methods eliminate the attractant from airfields
completely and make strides toward reducing overall wildlife strike risk.