1) The 2 verses that describes Noah’s ‘olah’ use terminology of Sefer Yayikra. The term ‘rayach nichoach’ especially. It’s also a very abrupt shift – Elokim to Havaya for the Korban (korbanot always have shem havaya) and immediately beck to Elokim. Korban terminology, in the DH, is much later, from the P source, whereas the flood story is a classic ‘J/E’ couplet. These 2 verses are a problem for the DH.
2) When God re-establishes His covenant w/ Noah, the Torah exclusively uses the name Elokim. DH scholars see the 2 accounts of covenants w/ Abraham from next week’s parsha as being a J/E couplet; the brit bein habetarim being an E source, and Brit Milah from a J source. However, the Brit Milah episode is much more closely linked, textually and thematically, to the covenant established w/ Noah, which ostensibly is from a different source.
Considering that the flood narrative is ostensibly the neatest couplet in the entire Torah, the fact that the DH runs into problems even here can give a decent impression of the difficulties w/ the theory in general.