american samoa - University of Hawaii at Manoa Botany Department

Option 2: Construct Basaltic Wall, Stabilize East Stream Bank,and Enhance Riparian VegetationIn the vicinity of station L6, a trench would be excavated along 300 linear feet of the drainagearea. The trench would be located immediately west of existing residences on the east side ofthe Leafu Stream drainage (Figure 9-4).A basaltic rock wall would be constructed within the trench using wire gabions approximately4x3x10-feet in size. Presence of the wall would better define the east stream bank and helpdirect future stream flows. At the same time, the wall may also help reduce potential flooddamage from medium stream flows. However, stream hardening along the east stream bankcould also generate an increase in stream flow velocities during stormwater events.Some basaltic rock treatment would be made on the top and east side of the wall to ensure thatthe wall would be attractive and complement existing residential and subsistence agriculturaldevelopment. The wall would also be back-filled with native soil on the east side of the wall toreduce the visual impact of the wire gabions (Figure 9-4).West of the proposed wall, the east stream bank would be enhanced through the planting ofroughly 100 native riparian trees such as ifi (Tahitian chestnut) fau, laufala, and falaga. Suchplants would increase the stability of the east stream bank that adjoins residential properties.The propagation of seeds and/or collection of tree cuttings would be made by the ASCC LandGrant Program nursery and planted by Land Grant personnel in cooperation with locallandowners.Option 3: Stabilize East Stream Bank and Enhance Riparian VegetationOption 3 would be very similar to Option 2 except that no basaltic wall would be constructed tobetter define the margin of the east stream bank near L6. Otherwise, the same type and numberof native riparian trees would be planted along portions of the east stream bank near L6 (Figure9-5).The establishment of ifi (Tahitian chestnut), fau, laufala, and falaga and other native ripariantrees along the east stream would primarily help stabilize the east bank that adjoins residentialand subsistence agricultural land uses. The root systems associated with these trees containroots that can effectively help stabilize the soil.The propagation of seeds and/or collection of tree cuttings would be made by the ASCC LandGrant Program nursery and planted by Land Grant personnel in cooperation with locallandowners. However, the ASCC Land Grant Program may elect to encourage adjoiningresidents to participate in the planting of these trees along the east stream bank.ASCC Land Grant has considerable experience with encouraging community participationthrough its Forestry Stewardship Program. Colin Steele, ASCC/AHNR project forester,envisions that the establishment of native riparian trees and the related participation of residentscan best be accomplished by providing, at no charge, a total of 30 tree seedlings to eachhousehold along the stream. However, the “no charge” arrangement would be conditional tothe resident’s agreement to plant the new trees within 30 feet of the stream bank (Steele, 1995).Consequently, some 100 riparian tree plantings would be randomly planted along the east bank,roughly 300-550 feet upstream of the stream mouth.American Samoa Wetlands/Streams Restoration and Enhancement PlanFebruary 2001, Leafu Stream, Page 9-11