a swath of

静岡県浜松市で運搬ルート周辺に住む約３８００世帯・約１万人に避難指示が出され、大規模な不発弾の処理が行われました。東海道新幹線も一時、運行をストップしました。

Bomb squad digs local beach to explode shell

Residents evacuated a swath of the central Japanese city of Hamamatsu today and bullet train runs halted for an hour as military explosives experts detonated a World War II-era artillery shell at a local beach.

Almost 70 years after the war, Ground Self-Defense Force bomb squads are still clearing unexploded ordnance throughout the nation, including in central Tokyo. They've dealt with some 6,000 tons of duds since the government began keeping records in 1958, according to defense ministry records.

Hamamatsu evacuated about 10,000 residents and halted rail and road traffic as this latest dud, an 860-kilogram (1,900- pound) shell probably fired by a U.S. Navy ship, was transported to the beach, according to a statement by the city government. The bomb squad exploded it at 2 p.m. local time.

http://newsonjapan.com/html/newsdesk/article/101016.php

swathは「ひと刈り分の牧草」という意味ですが（cf. swathe）、ここではa swath ofで、東海道新幹線から南にむけて、大規模に刈られたような「広大な帯状の避難地域」のことを指します。
昨日の会議に西日本から来られた先生方は飛行機などで新幹線ストップによる遅れを回避されていました。（UG）