Erosion and Sediment Control - Faga’alu, American Samoa

Outline

Introduction and Objectives -

American Samoa -

Stream Sampling -

Land-Based Sources of Pollution -

Impacts -

Environmental Management Practices -

Summary -

Acknowledgements -

Introduction

• Steven Curtis

• The Pennsylvania State University

• Environmental Meteorology

• National Ocean Service (NOS)

– Fagatele Bay National Marine Sanctuary (FBNMS)

Introduction

• FBNMS a member of the Governor’s Coral Reef Advisor Group (CRAG)

• Addressed Land-Based Sources of Pollution to mitigate impacts on coral reef within Faga’alu Bay, American Samoa

• Supports NOAA’s objective

• Emily Gaskin (FBNMS) • Lauren Wetzell (AS-CMP) • Phil Wiles (AS-EPA) • Hideyo Hattori (CRAG Lead) • Rocco Tinitali (ASCC)

American Samoa

• Consists of Five (5) Islands

• Latitude / Longitude: 14.30S 170.70W

• Population: ~60,000

• Capital City: Pago Pago

• Faga’alu Village

http://www.nationsonline.org/map_small/samoa.jpg http://www.infoplease.com/atlas/state/americansamoa.html

Faga’alu

Faga’alu

• Population: 1,006

• Rainfall: 155-165 inches / year

• Nestled in valley of Matafao Peak

• Observable impacts from sediment throughout stream and on reef flat

• During heavy rain events, the problem was exacerbated

Objectives

• Hypothesis: There are statistically significant land-base sources of sediment that affect the stream and coral

• Identify potential land-based sources of pollution

• Statistically significant contributors of sediment to Faga’alu Stream

• Suggest environmental management practices to mitigate impacts on coral reef

Methods

• Participatory, Learning, and Action (PLA) – Community outreach

– Understand potential land-based sources of sediment

– Educate community and promote environmental stewardship

• Worked with intern at American Samoa Community College to help build local capacity

• Supports NOAA’s objective on “engaging local stakeholders in coastal and marine management planning” while improving “community readiness to cope with natural and human-induced coastal hazards.”

Methods

• Identify potential land-based sources of sediment

• Utilize YSI Sonde to measure turbidity

• Turbidity – measured in Nephelometric

Turbidity Units (NTU)

– The sensor uses optics to calculate the clarity of the water.

– Often used as an indicator of how much sediment is in the water.

• Land-Based Sources of Pollution

• LBJ Hospital

• Bridge and Road Construction

• Quarry

• Matafao Landslide

• Nine (9) Sample sites were selected

• Study commenced June 2, 2011

• Two-Hundred Fifteen (215) samples

Sampling Strategy

Site #9

Site #8

Site #7

Site #6

Site #5

Site #2 & 3

Site #4

Site #1

• Clean Water Act states turbidity measurements SHOULD NOT exceed FIVE (5) NTU

• Turbidity measurements ranged from 0 – 735 NTU

• One-Hundred Ten (110) out of Two-Hundred Fifteen (215) samples failed ASEPA Standards

Results

• Statistics

– Descriptive Statistics

– Box-and-Whisker Plots

– Kruskal-Wallis Test

– Mann-Whitney Test

Results

• Quarry and Construction have the HIGHEST mean and median turbidity measurements

• Sample sites upstream from the quarry have lowest turbidity measurements

Matafao landslide may not be significant source of sediment

Results

• Kruskal-Wallis Test

– Compares median turbidity measurements between ALL site

• Are sample populations the same or do other factors influence turbidity measurements?

Results

• Given the Kruskal-Wallis test, with 95% confidence, we can accept the alternative hypothesis that the sample sites have differing median values and do not belong to the same population.

• Suggests that there are factors influencing turbidity measurements

Results

• Mann-Whitney Test – Similar to a rank-sum test, a non-parametric test to

determine if two samples differ

– Used to determine if two sample sites have statistically different turbidity measurements

– Test utilized to assess whether QUARRY or CONSTRUCTION are statistically significant sources

Results

Results

Quarry

• With 95% confidence, we can accept the alternative hypothesis that turbidity measurements at the quarry tend to be greater than the turbidity measurement above the quarry

= Quarry is a statistically significant source of sediment

Results

Construction

• With 95% confidence, we can accept the alternative hypothesis that turbidity measurements at the construction site tend to be greater than the turbidity measurement upstream

= Construction is a statistically significant source of sediment

Impacts - Construction

• Construction can increase erosion

upwards of 200 times that of vegetated

land (Georgia Soil and Water Conservation Commission)

• Uncovered land increases runoff directly into the stream culvert

Impacts - Quarry

• Uncovered land increases impacts of erosions

• Other impacts:

• Loss of habitat

• Noise

• Dust and air quality

• Chemical spills and heavy metals

Impacts – Faga’alu Bay

• Sediment enters the bay continually from the stream

• Settles and destroys coral habitat

• Siltation harms coral and transition from coral dominated to algal dominated community

Environmental Management Practices

• Riparian zone in need of management practices

• Coastal Vegetation – Vetiver Grass

• Sediment Traps

• Organic Matter Cover

• Silt Fences

http://www.flickr.com/photos/normvanthoff/sets/72157622408840550/detail/ http://midwestboatparty.com/forum/showthread.php?23264-Acreage-Home-Construction-Project

Environmental Management Practices

• Ideally, in order to be in compliance with American Samoa Environmental Protection Agency protocol, the quarry should move machinery to at least fifty feet from the stream bank.

Follow-Up

• My research has alerted CRAG and the PNRS Board.

• Beginning enforcement of environmental management practices throughout the island

• PNRS Board reviewing quarry and construction permit

• Quarry and construction representatives asked to conduct Environmental Assessment and make improvements of management practices or permit will be revoked

Summary

• The QUARRY and CONSTRUCTION are statistically significant sources of land-based pollution

• Steps are being taken throughout community to mitigate impacts of land-based sources of pollution

• Project succeeding in addressing key NOAA mandates from the National Marine Sanctuaries Act, the Coastal Zone Management Act, and the Coral Reef Conservation Act

Acknowledgements

NOAA Office of Education

Lauren Wetzell (ASCMP)

Emily Gaskin (FBNMS)

Phil Wiles (ASEPA)

Christin Reynolds

(GIS Lead)

Hideyo Hattori (CRAG Lead)

Rocco Tinitali

NOAA

AS-DOC

FBNMS

AS-EPA

References • American Samoa Department of Commerce.

(2006). Statistical Yearbook 2006. Retrieved 6 29, 2011, from Statistics Division: http://www.spc.int/prism/country/as/ stats/fnl06yrbkhome.pdf

• Craig, P. (2009). Natural History Guide to American Samoa. In P. Craig (Ed.). Pago Pago: National Park Service.

• DiDonato, G. T. (2005). Nitrogen and phosphorus concentrations in tropical Pacific insular streams: historic data from Tutuila, American Samoa. Micronesica , 37 (2), 235-247.

• Georgia Soil and Water Conservation Commission. (2002). Erosion and Sediment Course Manual .

• Hirsch, D. H. (2010, March 23). Statistical Methods in Water Resources. Retrieved July 13, 2011, from USGS: http://pubs.usgs.gov/twri/twri4a3/ht ml/pdf_new.html

• Langer, W. H., & Arbogast, B. F. (1998). Environmental Impacts of Mining Natural Aggregate. In A. G. Fabbri, G. Gaal, & R. B. McCammon (Eds.), Deposit and Geoenvironmental lModels for Resource Exploitation and environmental Security (pp. 151-168). Netherlands: Kluwer Academic Publishers.

• US Environmental Protection Agency. (2010, February 26). Water. Retrieved July 13, 2011, from http://water.epa.gov/lawsregs/lawsgu idance/cwa/tmdl/overview.cfm

• Wong, M. (1996). Analysis of Streamflow Characteristics for Streams on the Island of Tutuila, American Samoa. Honolulu: U.S. Geological Survey.

Kruskal-Wallis Test

• Null Hypothesis (Ho) = All the sample sites have no variation amongst measurements

• Alternative Hypothesis (Ha) = At least one sample site has a different distribution and the sample comes from different populations.

Degrees of Freedom

Χ20.95(8) K

8 15.51 142.18

Mann-Whitney Test

• Null Hypothesis (Ho): Turb(Site#6) = Turb(Site#7) The turbidity values measured downstream the quarry are equal to those turbidity values measured above the quarry

• Alternative Hypothesis (Ha): Turb(Site#6) > Turb(Site#7) Turbidity values measured downstream of the quarry tend to be higher than those turbidity values measured at above the quarry

U-value Z-score(0.95)

Converted Z-value

594 1.645 5.87

Mann-Whitney Test (2nd)

U-value Critical U-Value

25 <25

• Null Hypothesis (Ho): Turb(Site#5)= Turb(Site#7) The turbidity values measured downstream the construction are equal to those turbidity values measured above the quarry

• Alternative Hypothesis (Ha): Turb(Site#5) > Turb(Site#7) Turbidity values measured downstream of the construction tend to be higher than those turbidity values measured at above the quarry