Bird Collision Risk

Use of Avoidance Rates in the SNH Wind Farm Risk Collision Model

Blair Urquhart, Policy & Advice, Scottish Natural Heritage, 2010.

The SNH Collision Risk Model (CRM) provides an estimate of the potential number of bird collisions likely to occur at a proposed wind farm. Birds react to a wind farm in different ways. Some may be displaced from the area of the wind farm, while others may avoid turbines or take other evasive action to prevent a collision. The CRM first estimates the number of collisions that would occur if the birds were to take no avoidance action. It then applies an avoidance rate to take account of the likely degree of successful avoidance.

Calculating a Theoretical Collision Risk Assuming no Avoiding Actions

Guidance Note Series, Scottish Natural Heritage, 2000

Windfarms may impact on ornithological interests in a number of ways. There may be: loss of habitat due to the construction of turbine bases and tracks, displacement of birds as a result of disturbance, and potential mortality through collision. SNH Guidance note describes a methodology for assessing in full the impact of windfarms on ornithological interests, taking account of each of these effects. The methodology includes a two-stage process for the assessment of collision risk.

The purpose of this document is to compare the bird collision analysis method and equation employed by Scottish Natural Heritage (SNH) for horizontal axis wind turbines (HAWTs) with those that were derived from a similar method for vertical axis wind turbines (VAWTs). WHI repurposed SNH’s equations, approximations, assumptions and techniques, which SNH described for determining the frequency of bird strikes for HAWTs.

WHI’s VAWT-Bird Collision Calculator

Matt Wylder, Wind Harvest International, August 2014

WHI commissioned UCD engineer Matt Wylder to take the Scottish Natural Heritage model for calculating bird strikes in HAWTs and redo it for VAWTs.    His paper “Vertical Axis Wind Turbines and Birds:  Calculating a Theoretical Collision Risk Assuming No Avoiding Action” summarizes a number of runs he made using the VAWT collision model he developed.  We welcome people to use and improve upon this tool.

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