Identifying Best Management Practices for Reducing Mauka Stream Sediment in Maunalua Bay

Abstract

Maunalua Bay is a 22 square mile region extending from the southern tip of Diamond Head or Kūpikipikiʻō on the west to Kawaihoa Point to the east. The area consists of 10 watersheds and 6.5 square miles of ocean waters, and historically was a prominent fishing and limu (seaweed) gathering place (Mālama Maunalua 2009). However, in recent decades the region has undergone dramatic urbanization; its numerous channelized and cemented streams being one of the main signs of the region’s developed nature. Wailupe Stream is the only non-cemented stream of the ten major streams in the Maunalua Bay region (Mālama Maunalua 2009). Channelized and cemented streams prevent property damage by efficiently removing stormwater from urban areas, but increase sediment levels in Maunalua Bay which decreases ecosystem health and lowers water quality (Wagner 2011, Nunnally 1978). Since much of Maunalua Bay consists of residential and commercial areas, space and liability issues regarding both construction activities and potential flooding is a major factor when considering which stream sediment management methods are feasible. Previous projects have already investigated the potential of implementing sediment reduction BMPs within the residential zones of Maunalua. Past projects that have also focused on homeowner education to reduce impervious surfaces and create household sediment buffers have tried to address this issue in residential areas (Wagner 2011). The purpose of this project is to review Best Management Practices (BMPs) to reduce stream sediment in the upper regions of the watershed and identify BMPs that would be feasible to establish in three main Maunalua Bay streams (Kuliouou, Niu, and Wailupe) under time and money constraints. This information will allow Mālama Maunalua, a community-based, non-profit stewardship organization, to combat excessive stream sedimentation and the resulting negative impacts on the region’s ecosystem.