american samoa - University of Hawaii at Manoa Botany Department

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ate maps prepared by FEMA suggest that residential properties along the east and west banksof the Asili Stream segment could be flooded from a 100-year storm event. FEMA alsoindicates that culvert underneath the Route 1 bridge is capable of containing flows from a 100-year storm event.Surface Water QualityDuring its November 1999 survey, PPC representatives informally met with Mr. Tago, avillage matai and member of the Fono. Mr. Tago reported that a significant amount ofsediment is discharged from Asili Stream during and following storm events. He believes thatturbid surface water discharges are due, in part, to erosion occurring in upland areas of thevillage that are used for the production of various subsistence crops.From October 1995 through May 1996, ASEPA conducted a water quality monitoring programat selected streams in Asili, Leone and Afono. This program was aimed at gaining a betterunderstanding of the source of sediments that impact surface water quality in the selectedstreams.Along each stream, weekly samples were obtained from stream locations that were adjacent todeveloped lands, a plantation, and undeveloped lands. Water samples were subsequentlyanalyzed to determine concentrations of total suspended solids (TSS), turbidity, total nutrients,and total phosphorus.Data obtained from this water quality monitoring program did not detect any significantdifference in water quality between the three types of stations along Asili Stream.Consequently, it remains unclear whether or not upstream plantations are contributing anysignificant amounts of eroded soil material into Asili Stream.VEGETATIONNovember, 1999 SurveyArt Whistler of Isle Botanica conducted a botanical survey of the Asili Stream segment onNovember 10, 1999. The walk-through survey was made within the stream banks from station1+00 and station 10+00 (Figure 10-2). Mr. Whistler was part of a three-person field surveyteam organized by Pedersen Planning Consultants that observed wetland vegetation, habitat foraquatic fish and invertebrates, stream hydrology, as well as land uses within and adjacent to thewetland. His observations are summarized in the following paragraphs.The vegetation of Asili Stream was comprised ofplants growing along the stream banks. One exceptionis the small “island” along the west stream bank that issituated immediately upstream of the most upstreamhome in Asili Village. The “island” was covered withdense herbaceous vegetation dominated by vao lima(T-grass). Less amounts of Malay ginger (Costusspeciosus) and taamu (giant taro) were interspersedwith banana trees and laupata (Macaranga harveyana). Taamu (giant taro, Alocasia macrorrhiza)The edge of subsistence plantations were adjacent to the stream banks in the vicinity of stations9+00 and 10+00. This area was dominated by plantation trees and weeds that are notcharacteristic of wetlands.American Samoa Wetlands/Streams Restoration and Enhancement PlanFebruary 2001, Asili Stream, Page 10-6
Further downstream, the stream channel becomes more narrow and rocky. Native forest treesalong the east and west stream banks included afa (Neonauclea forsteri), fuafua (Kleinhoviahospita), fau (beach hibiscus), and maota mamala (Dysoxylum samoense). Wetland trees suchas ifi (Tahitian chestnut) and falaga (Barringtonia samoensis), as well as cultivated trees suchas ulu (breadfruit) also dominated this area. The ground cover consisted of basket grass, T-grass, and various weeds that are characteristic of upland vegetation.Lands adjacent to the lower portion of AsiliStream were more disturbed and containedcultivated trees such as vi (Polynesian plum),beach hibiscus, coconut, and breadfruit. Rockwalls, concrete walls, and rock-filled gabionbaskets reinforced most of the stream banks.Where man-made flood control structures werenot present, barren soils and soils covered withweeds were observed. Some landscaped lawnsalso were also established immediately abovethe stream banks.Between the stream mouth and the Route 1 bridge, a more lagoon type of environment wasevident. The seaward side of the stream channel contained modified littoral vegetation.Vegetation TrendsNo prior studies of the vegetation of Asili Stream have been conducted. Consequently, nocorrelation can be made concerning historical vegetative trends.The Asili Stream segment was probably once dominated by the same species that wereobserved upslope of the village. This vegetation comprises trees such as afa (Neonaucleaforsteri), fuafua (Kleinhovia hospita), fau, and maota mamala (Dysoxylum samoense).Wetland trees such as ifi and falaga are also present upstream of the village.The upper portion of the Asili Stream segment will probably remain in disturbed vegetation aslong as residents continue to harvest and use crops from subsistence plantations. The middleand lower portions of the stream segment are also expected to remain generally the same.However, the amount of vegetation along the stream banks may diminish somewhat if residentscontinue to build more flood control structures in response to future storm events.AQUATIC FISH AND INVERTEBRATESGeneralOn November 10, 1999, Charles Chong of the PPC field survey team made observations ofaquatic fish and invertebrates along the 1,000-foot segment of Asili Stream. His observationsare summarized in the following paragraphs.An overstory canopy covered much of the stream channel between the stream mouth and theinhabited residential area along the stream. Upstream of the village, the canopy over the streamwas more open.American Samoa Wetlands/Streams Restoration and Enhancement PlanFebruary 2001, Asili Stream, Page 10-7
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Asili StreamAMERICAN SAMOAWETLAND/S
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American SamoaWetland/Stream Restor
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American Samoa Wetland/Stream Resto
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Figure 1-1Location of Potential Wet
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Onsite InvestigationsNovember 1999G
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Where appropriate, stream cross sec
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Chapter TwoTULA WETLANDLOCATIONTula
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Figure 2-2Tula WetlandExisting Cond
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Improved channelization of stormwat
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LAND USES IN THE VICINITY OF TULA W
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Figure 2-3Option 2: Detention of St
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Figure 2-4Option 3: Expansion of Ta
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Comparative Benefits and ImpactsPPC
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TABLE 2-4PRELIMINARY COST ESTIMATEP
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TABLE 2-5LONG-TERM RESOURCE MONITOR
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TABLE 2-6 (CONTINUED)FIELD MONITORI
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Chapter ThreeALAO WETLANDLOCATIONAl
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Figure 3-2Taufusi MarchExisting Con
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Figure 3-3FEMA 100-Year Flood Plain
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East Portion of the MarshThe impact
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WETLAND RESTORATION AND ENHANCEMENT
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The availability of new, blight-res
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Long-Term Monitoring and Site Maint
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TABLE 3-7FIELD MONITORING WORKSHEET
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Recommended monitoring stations or
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Figure 4-1Location MapAoa Village W
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No stream flow estimates are availa
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Fresh-Water SwampThe fresh-water sw
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ecome dominant if there is a nearby
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Relative Abundance and Diversity of
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Option 4: Restore Mangrove Forest U
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TABLE 4-5COMPARATIVE EVALUATIONWETL
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Long-term resource management activ
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• begin at the Tapua Stream mouth
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Figure 5-1Location MapSoutheast Wet
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Tufu Stream and two stream branches
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Mr. Whistler was part of a three-pe
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InvertebratesCrustacean densities w
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FIGURE 5-3OPTION 1: RESTORE RIPARIA
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TABLE 5-4COMPARATIVE EVALUATIONWETL
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Long term monitoring of the Vatia w
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More specific monitoring of stream
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Figure 6-1Location MapVaipito Strea
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Stream FlowsHistorical Stream Flows
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California grass (Brachiaria mutica
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FIGURE 6-3FISH AND INVERTEBRATE SUR
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Most of lower Vaipito Stream segmen
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Red mangrove should be planted with
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TABLE 6-7PRELIMINARY COST ESTIMATEC
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TABLE 6-9LONG-TERM RESOURCE MONITOR
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TABLE 6-10 (Continued)FIELD MONITOR
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Vehicular and pedestrian access to
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Figure 7-1Location MapLeele-Papa-Ta
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Stream flow, in some cases, is cons
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Stormwater Discharges and Related F
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AQUATIC FISH AND INVERTEBRATESGener
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Opportunities and StrategiesOption
Page 123 and 124: Figure 7-3Option 2: Reduction of Er
Page 125 and 126: TABLE 7-8PRELIMINARY COST ESTIMATEP
Page 127 and 128: TABLE 7-9LONG-TERM RESOURCE MONITOR
Page 129 and 130: TABLE 7-10 (Continued)FIELD MONITOR
Page 131 and 132: More specific monitoring of stream
Page 133 and 134: Figure 8-1Location MapSauino Stream
Page 135 and 136: Stream FlowsHistorical Stream Flows
Page 137 and 138: AQUATIC FISH AND INVERTEBRATESGener
Page 139 and 140: Figure 8-3Option 1: Construction of
Page 141 and 142: FIGURE 8-5OPTION 2: PLANT NATIVE RI
Page 143 and 144: Long-Term Monitoring and Site Maint
Page 145 and 146: TABLE 8-8FIELD MONITORING WORKSHEET
Page 147 and 148: TABLE 8-8 (Continued)FIELD MONITORI
Page 149 and 150: LOCATIONChapter NineLEAFU STREAMLea
Page 151 and 152: Figure 9-2Leone Pala and 300-Foot L
Page 153 and 154: However, during and following heavi
Page 155 and 156: Vegetation TrendsThe lower Leafu St
Page 157 and 158: LAND USES ADJACENT TOLOWER LEAFU ST
Page 159 and 160: Option 2: Construct Basaltic Wall,
Page 161 and 162: Figure 9-5:Stabilize East Stream Ba
Page 163 and 164: TABLE 9-7PRELIMINARY COST ESTIMATEP
Page 165 and 166: TABLE 9-8LONG-TERM RESOURCE MONITOR
Page 167 and 168: TABLE 9-9 (Continued)FIELD MONITORI
Page 169 and 170: Chapter TenASILI STREAMLOCATIONAsil
Page 171 and 172: Figure 10-2Asili Stream SegmentExis
Page 173: Stormwater Discharges and Related F
Page 177 and 178: TABLE 10-4SUMMARY OF MACROFAUNAL OR
Page 179 and 180: American Samoa Wetlands/Streams Res
Page 181 and 182: CLEAN-UP OF LOWER ASILI STREAMLABOR
Page 183 and 184: TABLE 10-9LONG-TERM RESOURCE MONITO
Page 185 and 186: TABLE 10-10 (Continued)FIELD MONITO
Page 187 and 188: Vehicular and pedestrian access to
Page 189 and 190: Figure 11-1Location MapFusi Wetland
Page 191 and 192: WETLAND VEGETATIONNovember 1999 Sur
Page 193 and 194: The lack of stream flow entering th
Page 195 and 196: Figure 11-3Option 1: Remove Solid W
Page 197 and 198: Recommended Option and Estimated Pr
Page 199 and 200: TABLE 11-6FIELD MONITORING WORKSHEE
Page 201 and 202: Any future monitoring stations or s
Page 203 and 204: Project ManagerRepresentatives of a
Page 205 and 206: REFERENCESBiosystems Analysis, Inc.
Page 207 and 208: APPENDIX ASUMMARY OFPLANTSOBSERVED
Page 209 and 210: Species Family EnglishNameSamoanNam
Page 213: APPENDIX CSUMMARY OFAQUATIC MACROFA
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