The speaker is looking at what a flood leaves behind: mold creeping through the closet and clothes too damaged to save. The details are small and domestic, which makes the loss feel close and personal rather than huge and distant.
The turn comes with "her fine linen green / as water." The poem seems to shift from the speaker's own ruined clothes to someone else's linen, now stained green, or perhaps green in color like the flood itself. The final line, "that run-away bride," is the poem's most striking image. Judging by the wording, the water itself might be the bride, slipping away after doing its damage, or the linen might suggest a bridal dress. The poem doesn't settle this, and the ambiguity is part of its pull.
The mood is quiet, wistful, and a little eerie. The speaker doesn't shout about the loss. Instead, the sparse lines and abrupt breaks leave a sense of absence, as if something beautiful and delicate has vanished along with the water.