I have what looks like a hole in my DEM! I don't think it is affecting my calculations, but either way, I would quite like to correct it.
Does anybody have any idea how?
Please see the attached picture to understand what I mean.
I had the same problem using some SRTM DEMs. Besides from using some later and more correct version or another data source, I'd recommend setting all values below some chosen threshold (that will only select the hole pixels) to NoData (=erase them) and then re-interpolating them according to the surrounding pixels so that there will at least be no excesses.