Pollution in the Ala Wai Canal

This project focuses on the pollution of the Ala Wai Canal located in Oahu, Hawaii. It talks about how these stormwater conduits and streams play a key role on the pollution of the canal, with hopes to reduce plastics that go with stormwater into the ocean. The purpose of this project is to inform the audience about the problems our waterway currently experience to this day and it shows different solutions on how we should face this.

The Ala Wai Canal is an artificial waterway located in Honolulu, Hawaii. Construction started in 1921 and ended in 1928. It was built to drain rice paddies and swamps which once existed in the Waikiki area.

Urbanization had brought pollution problems into the Ala Wai Canal. Runoff from the streets and fast growing neighborhoods, adding trash and chemicals, flow downstream from Makiki, Palolo, and Manoa Streams into the canal and out into the boat harbor. The Ala Wai is filled with bacteria, heavy metals, pesticides, and other pollutants hazardous to our health.

1929 - Warning issued: Canal is unsafe for swimming 1965 - Canal overflows and floods Waikiki 1967 - Canal floods Waikiki again. Canal dredged for first time 1991 - Department of Health posts signs: Do not fish or swim in canal 2006 - Man dies of massive bacterial infections after falling in the Ala Wai

There are 3 major streams that enter the Ala Wai Canal: Manoa, Palolo, and Makiki Stream

Stormwater Conduits help prevent floods by diverting rainwater into nearby waterways such as the Ala Wai Canal. During rainstorms, water runs off of buildings, roads, and other hard surfaces, accumulating trash and pollutants along the way. The water and pollutants flow into these stormwater conduits directly into the nearest stream, pond, or waterway.

The Streams and Stormwater Conduits datasets were provided by Hawaii State GIS Program. Hawaii’s GIS Program is in charge of planning, coordinating, and maintaining geographic information systems(GIS) and associated geospatial databases within the State of Hawaii. I processed the Streams and Stormwater Conduits datasets by inputting the data into ArcGIS Pro in which I then deleted the unnecessary streams and stormwater conduits, the ones not connected with the Ala Wai Canal. After, I added points that represent where these streams and conduits enter the Ala Wai Canal.

The datasets used in the map above are the “Waikiki watershed" layer and DEM Imagery for Oahu from the School of Ocean and Earth Science and Technology (SOEST) of the University of Hawaii at Manoa. I processed these datasets by creating a surface flow accumulation layer which I then used to determine the flow direction of the waters. I used line thickness to represent the different values of flow accumulation.

The Flow Accumulation Map displays the accumulated water in a specific area of waterway. The thickness of the blue lines represent greater chance of flood and pollution input since there are more accumulation of water in it. Therefore, we can use this map to determine important drainage patterns into the Ala Wai Canal.

Major outlets that greatly contribute to the Ala Wai Canal are the Manoa-Palolo Drainage Canal and Makiki Stream. The Manoa-Palolo Drainage Canal is where Manoa Stream and Palolo Stream waters merge together and continue to the Ala Wai Canal.

Here are current and potential efforts that are being done by different programs that share the same mission, to restore the Ala Wai Canal.

The Genki Ala Wai Project is a non-profit project under the Hawaii Exemplary State Foundation. They are trying to use bioremediation technology to make the Ala Wai Canal fishable and swimmable within seven years.  

The Ala Wai Watershed Collaboration began work on an 18-month feasibility study of eight partner-led projects in early 2021.

A student-led water quality observation and sampling network at the University of Hawaii.

Green Infrastructures such as bioswales, retention basins, wetlands, rain gardens, and urban green spaces can be used to reduce flooding, augment surface water supplies, recharge groundwater, and improve water quality. Green stormwater infrastructure not only controls stormwater volume and timing but also promotes ecosystem services, which are the benefits that ecosystems provide to humans. Green infrastructure practices make cities act more like forests by capturing rainwater where it falls, filtering out pollutants, and reducing large volumes of runoff.

Kapakahi Stream, located in Waipahu, Hawaii,  flows from its headwaters, at the Hawaii Plantation Village, to the West Loch of Pearl Harbor.  Despite the fact that Kapakahi Stream is polluted with plastics, the water is still clear. This is because of the plants around it that filters the water or acts like green infrastructure. Besides filtering the water, green infrastructure systems can deliver major value for the community by providing flood protection, diversified habitat, and even cleaner air.

In the case of the Ala Wai Canal, we can integrate green infrastructure such as rain gardens and bioswales. Rain garden, a depressed area in the landscape that collects rain water from a roof, driveway or street and allows it to soak into the ground, will be a good green infrastructure to include in the Ala Wai Canal because of it cost effective and a beautiful way of reducing runoff.

Bioswales, channels designed to concentrate and convey stormwater runoff while removing debris and pollution would also be a good green infrastructure because it can control runoff velocity and help to decontaminate runoff.

Because of the rising urbanization near the Ala Wai Canal, the level of pollution has grown. The streams also play a key role in the Ala Wai's pollution because of them being major inputs. Despite the situation, there is still a chance that it can be restored since there are many solutions out there that we can use. There are current projects that are coming up with their own solutions, many of them using new technologies. But, we should also consider integrating simple green infrastructure in the Ala Wai because of it effectiveness of controlling the stormwater runoff.