Up until the 1960’s most of North Kihei’s coastal plain was covered with many active wetlands. Prone to frequent flooding and home to wildlife. There were homes and buildings scattered along the beaches from sugar beach to Makena landing, but in-between and mauka stood many open fields, abandoned farmland, scrub areas, as well as the wetlands. As more people moved into Kihei, wetlands were neglected and began shrinking. In some cases they were actively drained, filled in, and covered over. Former taro patches and farmer’s fields became sites for home building and various construction projects. This trend continued with Kihei’s famous wetlands, streams and ponds, gradually shrinking year after year. Kihei still has some active wetlands, and in many areas till this day the water-table is just a few feet below the surface. After heavy rains, the water table can rise and flood low-lying areas from beneath. Freshwater streams still flow underground, and occasionally come to the surface, and may even break through the ground in places.
Wetlands and other undeveloped lands have become natural stormwater detention ponds that hold excess rainwater coming down the mountain. Wetlands have a large capacity to hold excess water and can allow the silty rainwater to filter down through the soil and enter the underground water table, and recharge the aquifer. Wetlands stay wet for two reasons, continued replenishment from surface water, streams, and continuous replenishment from underground water (springs).
Wetlands are used as dumping grounds for urban runoff: Sadly Kihei’s wetlands are also used as convenient places for developers to dump their unwanted stormwater runoff. It should be noted the stormwater runoff is not always clean, and can contain chemicals, oils, and materials from the streets and urban areas, that are carried along with it. These contaminants will end up in the wetlands, and eventually enter the ocean.
Wetlands will change in size: in the rainy season wetlands become larger and wetter. The increased rainfall in the catchment basins mauka side, bring more water to the wetlands. Wetlands expend to surrounding areas and a greater area is engaged in the detention of stormwater, and more ground surface is recruited into the natural filtration process. These natural expansions and contractions should be respected when determining the boundaries of wetlands, and to ensure that a large enough area around the perimeter of wetlands is also protected from development.
Ephemeral Wetlands: Some areas can be fairly dry most of the time, but will become wet and flooded during high rainfall. These temporary (ephemeral) wetlands are also important to the water cycle. Ephemeral wetlands are either the result of surface runoff or rising water tables during hydrologic cycles.
Wildlife Habitat: When ephemeral wetlands appear, wildlife habitat expands, and new feeding grounds appear. Wildlife exploits these areas as the opportunities present themselves. One example of opportunism are water birds like the Ae’o (Other common names include the Hawaiian black-necked stilt, the aeʻo, the kukuluaeʻo) and the Hawaiian Coot (also known as the ʻalae kea in Hawaiian), and the Hawaiian duck or koloa, that readily utilize these transient aquatic environments. Even the endangered Nene is seen frequenting Kihei’s wetlands at various times. It should be noted that many of Maui’s endemic waterfowl and shoreline birds are endangered, and some species have become extinct due to loss of habitat.
Wetland Losses: Development on wetlands has reduced total wetland areas. Wetland losses in Kihei, wetlands were determined to have decreased from 199 acres in 1965 to 83 acres in 2001.
Open areas need to be preserved: This area of the Kihei floodplain still has several undeveloped areas that act as natural detention basins, and they should be preserved for this important purpose. This natural system works better than man-made detention basins. And can provide a beneficial effect as a buffer and a filter to protect the nearshore ocean environment from the negative effects of siltification and contaminated rainwater runoff. Natural areas like these can also provide vital habitat for endemic and endangered local species, such as Blackburn’s Sphinx Moth and Hoary bat etc.
Water returns to the ocean: All water finds its way to the sea. There are two main pathways’ for stormwater to return to the sea. One is via surface runoff, which can be very damaging to the environment. The other way is by underground rivers and springs that flow into the ocean via springs on the seabed. Millions of gallons of water enter the nearshore ocean waters everyday from underground springs in a continuous cycle. Human activity is responsible for diverting the natural stream flows, and for paving over soils and earth preventing the absorption of rainwater and runoff. Anthropogenic changes to the environment usually result in a disruption of the natural cycles, and can have harsh impacts on the nearshore environments, including the wetlands, and the nearshore waters.