Updated

Updated · Honolulu Star-Advertiser · Aug 21

Hawaii Island Issues Flood Watch as Tropical Depression Two-C Threatens 15 Inches of Rain

Updated

Updated · Honolulu Star-Advertiser · Aug 21

Hawaii Island Issues Flood Watch as Tropical Depression Two-C Threatens 15 Inches of Rain

Q: As Tropical Storm Moke approaches, what hidden dangers await Hawaii residents living in steep, mudslide-prone terrains this weekend?

The biggest hidden danger is fast-onset mudslides and debris flows, not just standing floodwater. On steep, slide-prone slopes of the Big Island, heavy rain from Tropical Storm Moke could quickly loosen already saturated soil left unstable by Hurricane Lala, sending mud, rocks, trees and runoff downhill with little warning. Forecasters say the Big Island could see 5 to 10 inches of rain, with isolated totals of 15 inches or more, especially on windward and southeast slopes and in steep terrain. The National Weather Service has warned that saturated ground will worsen runoff and raise the risk of flash flooding and mudslides from late Saturday night through Monday. For residents in hillside areas, the risk is that slopes can fail suddenly, cutting off roads, damaging homes, undermining foundations and trapping people with “no way in and no way out.” Even areas outside floodplains can be hit if water funnels through gulches, ravines or drainage channels below steep ground. Warning signs can be subtle and brief: new cracks in soil, leaning trees or poles, small trickles of muddy water, rumbling sounds, and rocks falling ahead of a larger slide. Strong gusty winds may also topple trees more easily because roots are sitting in waterlogged ground. Officials are urging residents in vulnerable terrain to monitor alerts closely, prepare to leave quickly if conditions worsen, avoid low spots and stream channels, and not drive across flooded or debris-covered roads.

3 articles · Updated · Honolulu Star-Advertiser · Aug 21

A flood watch will take effect late Saturday night through Monday afternoon for all Hawaii Island districts as Tropical Depression Two-C approaches on already saturated ground.
The system was 745 miles southeast of Hilo at 5 a.m., moving west-northwest at 10 mph with 35 mph winds, and forecasters expect it to strengthen into a tropical storm later Friday.
Current forecasts show the center passing south of the Big Island this weekend, but still dropping 5 to 10 inches of rain there, with isolated totals up to 15 inches; East Maui could get up to 4 inches.
Officials warned that rapid runoff could worsen urban flooding and property damage, while strengthening tradewinds and building swells may trigger hazardous surf and life-threatening rip currents along east- and south-facing shores starting Saturday.
The storm is expected to track farther south than Hurricane Lala did last weekend, yet emergency officials are still urging residents statewide to prepare and sign up for alerts.