PROJECT ALERT NOTICE (HI) Moderate flooding in Guam

Date: Wed, 24 May 2023 19:59:05 EDT

Summary: Typhoon Mawar brought heavy rainfall across the Island of Guam resulting in moderate flooding over the last 24 hours.

Typhoon Mawar reached the Island of Guam late Wednesday evening (GMT+10hr) bringing 12 to 24 inches of rain during a 24-hr period that caused moderate flash flooding in most streams. No information is available at this time on property damages; however, significant power outages were reported across the island. PIWSC operates a network of 7 stream gages and 8 rain gages in Guam and all gages except for 1 rain gage were operational throughout the storm. Streamflow was below the peak of record at all gages which, for most gages, occurred during a typhoon in December 2002.

PIWSC does not have staff on Guam but will send staff to the island in early June to assess any damage to the gage network, verify peak stage observations at streamflow gages, conduct indirect surveys if possible, and perform calibration checks at all rain gages.