Samidare ni irie no hashi no ukinureba orosu ikada no kokochi koso sure - Kinyo Wakashu(English Translation & Meaning)

五月雨に入江の橋の浮きぬれば
下ろす筏の心地こそすれ

Roma-ji: Samidare ni irie no hashi no ukinureba orosu ikada no kokochi koso sure
English Translation: In the early summer rain
the bridge across the inlet
has come afloat,
so it seems to me a raft
being sent down the stream
Meaning: In the early summer rains the bridge over the inlet has floated up, and it feels as if it were a raft being sent downstream.
Commentary: Book Two Summer Poems 140

The summer rains have swollen the water until the bridge over the inlet has floated, and it seems like a raft being sent down the river. The rising flood is depicted through the witty likening of the floating bridge to a raft.
With this poem the sequence on the summer rains ends. Having layered images of rising water since poem 135, it closes as the bridge floats up and becomes like a raft.

First line, 'samidare ni', means because of the summer rains.
Second line, 'irie no hashi no', is the bridge spanning the inlet.
Third line, 'ukinureba', adds ba to the realis form of the perfective nu: since it has floated. It goes a step further than 'almost floating' in poem 138 in this book, showing the bridge actually afloat.
Fourth line, 'orosu ikada no', is a raft sent down the river, a comparison for the floating bridge.
Final line, 'kokochi koso sure', is a binding in which koso closes on the realis sure.
Source: Kinyo Wakashu
Prev Poem: Samidare wa oda no minakuchi te mo kakede mizu no kokoro ni makasete zo miru
Next Poem: Natsu no yo no niwa ni furishiku shirayuki wa tsuki no iru koso kiyuru narikere