Waimahaihai Wetlands

At the foot of the Waimahaihai Gulch where the stream meets the floodplain is an area of historically extensive wetlands that stretched from the Keokea Inlet at Laie Wetland all the way to the Cove at Kalama park. This entire area was the receiving basin for multiple streams (at least four of which are recognized in the DAR Drainage maps).  The streams fed a large wetlands zone that made these back-beach areas perpetually swampy bogs. Over time developers have filled in these areas, and drained these wetland zones, and channelized and diverted these streams. Although these areas are typically dry most of the time, they are still susceptible to extreme flooding. The wetland hydrology remains and the topography still directs the stormwaters into this coastal wetlands basin.

Waimahaihai: Waimahaihai is one of South Maui’s major named gulches has a large watershed (approximately 5445 acres) and is a significant streamway. This streamway has been identified in the KDMP as requiring significant flood management and recommended (albeit ill-conceived) drainage infrastructure improvements. Namely, diverting the entire Waimahaihai streamflow southward into the Kīhei Gulch and Kalama Wetland. 

Waimahaihai Keymap
Waimahaihai Watershed

About the Site: This site is within the study area, contains visible streamways and vegatative indicators, and meets the elevation and terrain criteria of the surrounding wetland study zone. This area is also within the 3.2ft SLR coastal hazard zone, and shares the aquifer with its neighboring wetlands. Waimahaihai Street also is home to a Hawaiian Fishing Heiau. Government GIS maps show the Waimahaihai stream actually forks on this site and splits into two streams that go toward the ocean.   

Fishing Shrine on Waimahaihai Street:

Viriditas, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons
14th century Hawaiian Koʻa i Kamaʻole Fishing Shrine. Viriditas, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons


Waimahaihai Fishing Shrine. Photo: S.Dorn

WAIMAHAIHAI orthophoto/Keymap (oriented north): The Waimahaihai orthophoto below shows several areas including stream beds and flood zones. The gulch pictured has a large riparian zone and open space areas with a canopy of mostly non-native vegetation, primarily Kiawe trees. This photo shows several distributaries of the mainstream streambed and several indications of wetland hydrology. The Waimahaihai stream bed below is located in the original Keokea Gulch, a major watershed feature.

This Gulch and Wetland system involves several TMK lots that include the stream bed, the floodplain, and the distributaries. The 10.5-acre lot just Mauka of South Kihei Road is the site of the original Waimahaihai stream and has been identified as the best location for a future mitigation wetland. The lot is also the widest portion of the streambed on the floodplain. The lots Makai of SKR are the stream’s distributaries.

Read More about the Waimahaihai Gulch Stream