Here's a couple of extracts from the Highland Council's own Flood Risk Management team responce to the planning officer responsible for the application:
"iii)The site drainage is to discharge into the Auldearn Burn to the south of the site. The Auldearn Burn has a history of flooding downstream in the area around Balmakeith Park and for this reason we require the post development runoff to be limited to the existing 2 year greenfield runoff rate. This has been calculated as 1.5 l/s."
iv). The current drainage proposals result in post development runoff rates of 2.5, 2.5, and 3.0l/s for 2, 30, and 200 year plus climate change return period storms respectively (taken from Appendix F of the SWMP). These rates equate to an increase in discharge over the existing greenfield rate for a 2 year storm, a slight betterment for a 30 year storm and a betterment for a 200 year storm.
v). As the current drainage strategy results in increased discharge over existing greenfield rates for the more frequent storm events we are not able to support the current drainage strategy and we raise an objection to the development.
Please note that submission of further information does not guarantee that the Flood Risk Management Team will be able to support this application. We reserve the right to request additional information in the determination of the application."
You can read the Flood Risk Management Team submission in full and other objections and statements of support on the Highland Council e-planning site here under the comments and document tabs here.
Gurn opinion: drainage will obviously be a serious stepping stone here for any future development at Balmakeith, the Auldearn Burn can indeed rise sharply during extreme weather events. Below are images from August 2014.