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Wetlands Regulatory Assistance Program

Regional Supplement to the Corps of Engineers Wetland Delineation Manual:

Hawai‘i and Pacific Islands Region (Version 2.0)

E nv ir on m en ta l L ab or at or y

U.S. Army Corps of Engineers February 2012

Approved for public release; distribution is unlimited.

N62742-21-R-1800 Attachment J-8

Wetlands Regulatory Assistance Program ERDC/EL TR-12-5 February 2012

Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Hawai‘i and Pacific Islands Region (Version 2.0)

U.S. Army Corps of Engineers

U.S. Army Engineer Research and Development Center 3909 Halls Ferry Road Vicksburg, MS 39180-6199

Final report

Approved for public release; distribution is unlimited.

Prepared for Headquarters, U.S. Army Corps of Engineers Washington, DC 20314-1000

ERDC/EL TR-12-5 ii

Abstract: This document is one of a series of Regional Supplements to the Corps of Engineers Wetland Delineation Manual, which provides technical guidance and procedures for identifying and delineating wet-lands that may be subject to regulatory jurisdiction under Section 404 of the Clean Water Act or Section 10 of the Rivers and Harbors Act. The development of Regional Supplements is part of a nationwide effort to address regional wetland characteristics and improve the accuracy and efficiency of wetland-delineation procedures. This supplement is applica-ble to the Hawai‘i and Pacific Islands Region, which consists of the state of Hawai‘i, the Territory of Guam, the Commonwealth of the Northern Mariana Islands, and the Territory of American Samoa.

DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes.

Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products.

All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.

DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.

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Contents Figures and Tables ................................................................................................................................. vi

Preface ....................................................................................................................................................ix

1 Introduction

Purpose and use of this regional supplement Applicable region Physical and biological characteristics of the region

The Hawaiian Islands

Guam and the Northern Mariana Islands

American Samoa

Types and distribution of wetlands

2 Hydrophytic Vegetation Indicators

Introduction Guidance on vegetation sampling and analysis

Definitions of strata Hydrophytic vegetation indicators

Procedure

Indicator 1: Rapid test for hydrophytic vegetation

Indicator 2: Dominance test

Indicator 3: Prevalence index

3 Hydric Soil Indicators

Introduction Concepts

Iron and manganese reduction, translocation, and accumulation

Sulfate reduction

Organic matter accumulation Cautions Procedures for sampling soils

Observe and document the site

Observe and document the soil Use of existing soil data

Soil surveys

Hydric soils lists Hydric soil indicators

All soils Indicator A1: Histosol Indicator A2: Histic Epipedon Indicator A3: Black Histic Indicator A4: Hydrogen Sulfide Indicator A8: Muck Presence

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Indicator A11: Depleted Below Dark Surface Indicator A12: Thick Dark Surface

Sandy soils Indicator S4: Sandy Gleyed Matrix Indicator S5: Sandy Redox Indicator S7: Dark Surface

Loamy and clayey soils Indicator F2: Loamy Gleyed Matrix Indicator F3: Depleted Matrix Indicator F6: Redox Dark Surface Indicator F7: Depleted Dark Surface Indicator F8: Redox Depressions

Hydric soil indicators for problem soils Indicator A5: Stratified Layers Indicator S1: Sandy Mucky Mineral Indicator F21: Red Parent Material Indicator TF12: Very Shallow Dark Surface

4 Wetland Hydrology Indicators

Introduction Growing season Wetland hydrology indicators

Group A – Observation of Surface Water or Saturated Soils Indicator A1: Surface water Indicator A2: High water table Indicator A3: Saturation

Group B – Evidence of Recent Inundation Indicator B1: Water marks Indicator B2: Sediment deposits Indicator B3: Drift deposits Indicator B4: Algal mat or crust Indicator B5: Iron deposits Indicator B7: Inundation visible on aerial imagery Indicator B9: Water-stained leaves Indicator B13: Aquatic fauna Indicator B17: Tilapia nests Indicator B6: Surface soil cracks Indicator B8: Sparsely vegetated concave surface Indicator B10: Drainage patterns

Group C – Evidence of Current or Recent Soil Saturation Indicator C1: Hydrogen sulfide odor Indicator C3: Oxidized rhizospheres along living roots Indicator C4: Presence of reduced iron Indicator C6: Recent iron reduction in tilled soils Indicator C7: Thin muck surface Indicator C10: Fiddler crab burrows Indicator C2: Dry-season water table Indicator C5: Salt deposits

Group D – Evidence from Other Site Conditions or Data

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Indicator D1: Stunted or stressed plants Indicator D2: Geomorphic position Indicator D3: Shallow aquitard Indicator D5: FAC-neutral test

5 Difficult Wetland Situations in the Hawai‘i and Pacific Islands Region

Introduction Lands used for agriculture Problematic hydrophytic vegetation

Description of the problem

Procedure

Problematic hydric soils Description of the problem

Soils with faint or no indicators Soils with relict or induced hydric soil indicators

Procedure Wetlands that periodically lack indicators of wetland hydrology

Description of the problem

Procedure Wetland/non-wetland mosaics

Description of the problem

Procedure

References

Appendix A: Glossary

Appendix B: Point-Intercept Sampling Procedure for Determining Hydrophytic Vegetation

Appendix C: Data Form

Report Documentation Page

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Figures and Tables

Figures

Figure 1. Location map of the Hawai‘i and Pacific Islands Region

Figure 2. Principal islands of the Hawai‘i and Pacific Islands Region

Figure 3. Coastal wetland on Kaua‘i dominated by Batis maritima and mangroves. Photo courtesy of the U.S. Fish and Wildlife Service

Figure 4. Aerial view of the Alakai Swamp, Kaua‘i, showing both forested and montane bog wetlands. Photo courtesy of the U.S. Fish and Wildlife Service

Figure 5. A soil sample from the Island of Hawai‘i containing structured (subangular blocky) sapric, folistic material at the surface and unstructured (homogeneous) sapric material below. Only the unstructured sapric material (muck) indicates soil saturation

Figure 6. Divergent slopes (A) disperse surface water, whereas convergent slopes (B) concentrate water. Surface flow paths are indicated by the arrows

Figure 7. At the toe of a hill slope, the gradient is only slightly inclined or nearly level. Blue arrows represent flow paths of surface water and groundwater

Figure 8. Example of a Histosol, in which muck (sapric soil material) is greater than 3 ft (0.9 m) thick

Figure 9. Thin organic soils (primarily Folists) are common over lava bedrock on the Island of Hawai‘i. However, saturated Histosols can be found on pāhoehoe flows in scattered depressions that trap and hold water

Figure 10. In this soil, the organic surface layer is about 9 in. (23 cm) thick. Scale is in centimeters

Figure 11. In this soil, a depleted matrix starts immediately below the black surface layer at approximately 11 in. (28 cm). Scale is in centimeters

Figure 12. Deep observations may be necessary to identify the depleted or gleyed matrix below a thick, dark surface layer. In this example, the depleted matrix starts at 20 in

Figure 13. In this example, the gleyed matrix begins at the soil surface. Scale is in inches on the right

Figure 14. Redox concentrations (orange areas) in loamy fine sand on the Island of O‘ahu

Figure 15. This sandy soil has a dark surface approximately 6 in. (15 cm) thick (bottom indicated by the arrow). Scale is in inches on the right side of the ruler

Figure 16. In this soil, a gleyed matrix begins immediately below the dark surface layer

Figure 17. Example of indicator F3 (Depleted Matrix), in which redox concentrations extend nearly to the surface

Figure 18. This soil has a depleted matrix with redox concentrations in a low-chroma matrix

Figure 19. Redox features can be small and difficult to see within a dark soil layer

Figure 20. Redox depletions (lighter colored areas) are scattered within the darker matrix.

Scale is in centimeters

Figure 21. In this example, the layer of redox concentrations begins at the soil surface and is slightly more than 2 in. (5 cm) thick

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Figure 22. Stratified layers in loamy material. Scale is in inches on the right

Figure 23. Stratified layers in sandy material. Scale is in inches on the right side of ruler

Figure 24. This mucky modified, sandy surface layer is approximately 3 in. (7.5 cm) thick.

Scale in inches on the right side of ruler

Figure 25. A wetland with surface water present, Waipi‘o Valley, Hawai‘i

Figure 26. High water table observed in a soil pit

Figure 27. Water glistens on the surface of a saturated soil sample

Figure 28. Water marks on rocks in a seasonally ponded depression

Figure 29. Water marks (dark stains) on trees in a seasonally inundated wetland. The top of one water mark is indicated by the arrow

Figure 30. Silt deposit left after a recent high-water event forms a tan coating on these tree trunks

Figure 31. Drift material caught on a fence and in low vegetation in a coastal wetland

Figure 32. Algal mat in a recently ponded depression, Kawainui Marsh, O‘ahu

Figure 33. Drying algal mat surrounding a ponded depression near the Saddle Road, Island of Hawai‘i

Figure 34. Dried crust of blue-green algae that has cracked and curled

Figure 35. Iron sheen on the water surface may be deposited as an orange or yellow crust after dewatering

Figure 36. Iron deposit (reddish area) in a taro patch

Figure 37. Aerial photograph showing inundation within an emergent wetland in the Ko‘olau Mountains on O‘ahu

Figure 38. Water-stained leaves in a coastal wetland

Figure 39. Water-stained hau (Hibiscus tiliaceus) leaves at Kawainui Marsh, O‘ahu

Figure 40. Remains of fiddler crabs (Uca spp.) in a coastal wetland. Fiddler crabs are found in American Samoa, Guam, and the Northern Mariana Islands, and are not known to occur in the Hawaiian Islands

Figure 41. Aquatic snails in a coastal wetland

Figure 42. Dead fish in a dried pool near Wai‘anae, O‘ahu

Figure 43. Cluster of tilapia nests in a shallow pond

Figure 44. Tilapia nest along the fringe of a drying pool near Wai‘anae, O‘ahu

Figure 45. Surface soil cracks (and drift material) in a coastal wetland

Figure 46. A sparsely vegetated depression in Batis-dominated coastal flats, northern O‘ahu

Figure 47. Vegetation bent over in the direction of water flow across a stream terrace

Figure 48. Iron-oxide plaque (orange coating) on a living root. Iron also coats the channel or pore from which the root was removed

Figure 49. Soil with oxidized rhizospheres surrounding many fine roots

Figure 50. When alpha, alpha-dipyridyl is applied to a soil containing reduced iron, a positive reaction is indicated by a pink or red coloration to the treated area

Figure 51. Redox concentrations in the tilled surface layer of a recently cultivated soil

Figure 52. Fiddler crab burrows and excavated soil

Figure 53. Salt deposits (light-colored areas) on coastal flats near Wai‘anae, O‘ahu

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Figure 54. Salt deposit at Kanahā Ponds, Maui

Figure 55. Stunted ‘ōhi‘a in Lehua Bog, Kaua‘i

Figure 56. Low areas behind coastal beach berms often exhibit wetland hydrology

Figure 57. Contact between surface soil and underlying saprolite for a soil on Guam. Saprolite can be a physical barrier to roots and often acts as an aquitard, perching water above it

Figure 58. Procedure and example of the FAC-neutral test. This example uses the same vegetation data as in Table 3

Figure 59. Effects of ditches (upper) and parallel subsurface drainage lines (lower) on the water table

Figure 60. This soil exhibits colors associated with reducing conditions. Scale is 1 cm

Figure 61. The same soil as in Figure 60 after exposure to the air and oxidation has occurred

Figure A1. Illustration of values and chromas that require 2 percent or more distinct or prominent redox concentrations and those that do not, for hue 10YR, to meet the definition of a depleted matrix. Due to inaccurate color reproduction, do not use this page to determine soil colors in the field. Background image from the Munsell Soil Color Charts reprinted courtesy of Munsell Color Services Lab, a part of X-Rite, Inc

Figure A2. For hydric soil determinations, a gleyed matrix has the hues and chroma identified in this illustration with a value of 4 or more. Due to inaccurate color reproduction, do not use this page to determine soil colors in the field. Background image from the Munsell Soil Color Charts reprinted courtesy of Munsell Color Services Lab, a part of X-Rite, Inc

Tables

Table 1. Sections of the Corps Manual replaced by this Regional Supplement for applications in the Hawai‘i and Pacific Islands Region

Table 2. Selected references to additional vegetation sampling approaches that could be used in wetland delineation

Table 3. Example of the selection of dominant species by the 50/20 rule and determination of hydrophytic vegetation by the dominance test

Table 4. Example of the prevalence index using the same data as in Table 3

Table 5. Proportion of sample consisting of fibers visible with a hand lens

Table 6. Determination of degree of decomposition of organic materials

Table 7. Minimum thickness requirements for commonly combined indicators in the Hawai‘i and Pacific Islands Region

Table 8. Example of a soil that is hydric based on a combination of indicators F6 and F3

Table 9. Example of a soil that is hydric based on a combination of indicators F6 and S5

Table 10. Wetland hydrology indicators for the Hawai‘i and Pacific Islands Region

Table A1. Tabular key for contrast determinations using Munsell notation

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Preface

This document is one of a series of Regional Supplements to the Corps of Engineers Wetland Delineation Manual. It was developed by the U.S. Army Engineer Research and Development Center (ERDC) at the request of Headquarters, U.S. Army Corps of Engineers (USACE), with funding provided through the Wetlands Regulatory Assistance Program (WRAP).

This is Version 2.0 of the Hawai‘i and Pacific Islands Regional Supplement;

it replaces the “interim” version, which was published in May 2010.

This document was developed in cooperation with the Hawai‘i and Pacific Islands Regional Working Group. Working Group meetings were held in Honolulu, HI, from 16-18 September 2008 and 11-12 February 2009.

Members of the Regional Working Group and contributors to this docu-ment were:

Jacob Berkowitz, Project Leader and Working Group Chair, Environ-mental Laboratory (EL), ERDC, Vicksburg, MS

Robert Lichvar, Chair, Vegetation Subcommittee, Cold Regions Research and Engineering Laboratory, ERDC, Hanover, NH

Chris Noble, Chair, Soils Subcommittee, EL, ERDC, Vicksburg, MS James Wakeley, EL, ERDC, Vicksburg, MS Greg Bruland, University of Hawai‘i at Mānoa, Honolulu, HI Benton Ching, U.S. Army Engineer District, Honolulu, HI Michelle Clark, U.S. Fish and Wildlife Service, Kapa‘a, HI Frank Dayton, U.S. Army Engineer Honolulu District, Guam

Regulatory Office, GU Fern Duvall, Hawai‘i Department of Land and Natural Resources, Wailuku, HI Terrell Erickson, U.S. Department of Agriculture (USDA) Natural

Resources Conservation Service, Washington, DC Robert Gavenda, USDA Natural Resources Conservation Service, Mongmong, GU Chris Jasper, USDA Natural Resources Conservation Service, Honolulu, HI Gregory Koob, USDA Natural Resources Conservation Service, Honolulu, HI Paula Levin, U.S. Fish and Wildlife Service, Honolulu, HI

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Tony Rolfes, USDA Natural Resources Conservation Service, Honolulu, HI

Lolly Silva, U.S. Army Engineer District, Honolulu, HI Christopher Smith, USDA Natural Resources Conservation Service, Washington, DC Gordon Smith, U.S. Fish and Wildlife Service, Honolulu, HI Wendy Wiltse, U.S. Environmental Protection Agency, Honolulu, HI

Technical reviews were provided by the following members of the National Advisory Team for Wetland Delineation: Steve Eggers, U.S. Army Engineer (USAE) District, St. Paul, MN; David Howard, USDA Natural Resources Conservation Service (NRCS), Washington, DC; Karl Hipple, NRCS National Soil Survey Center, Lincoln, NE; Dan Martel, USAE District, San Francisco, CA; Jennifer McCarthy, USAE District, New England, Concord, MA; Norman Melvin, NRCS National Wetland Team, Fort Worth, TX; Paul Minkin, USAE District, New England, Concord, MA; Stuart Santos, USAE District, Jacksonville, FL; Ralph Spagnolo, U.S. Environmental Protection Agency (EPA) Region 3, Philadelphia, PA; Mary Anne Thiesing, EPA Region 10, Seattle, WA; Ralph Tiner, U.S. Fish and Wildlife Service, Hadley, MA;

and James Wood, USAE District, Albuquerque, NM. In addition, portions of this Regional Supplement addressing soils issues were reviewed and endorsed by the National Technical Committee for Hydric Soils (Christopher W. Smith, chair).

Independent peer reviews were performed in accordance with Office of Management and Budget guidelines. The peer-review team consisted of Mike Lee, USAE Institute for Water Resources, Alexandria, VA (Chair);

Claudine Camacho, Dueñas, Camacho & Associates, Inc., Hagåtña, GU;

Susan M. Carstenn, Hawai‘i Pacific University and Tetra Tech, Inc., Honolulu, HI; Mark W. Defley, USDA Natural Resources Conservation Service, Mongmong, GU; Eric B. Guinther, AECOS, Inc., Kane‘ohe, HI;

Robert W. Hobdy, Hawai‘i Department of Land and Natural Resources, Haiku, HI; Penny Levin, Wailuku, HI; and Ron Terry, Geometrician Associates, LLC, Hilo, HI.

Technical editors for this Regional Supplement were Jacob F. Berkowitz, Robert W. Lichvar, Chris V. Noble, and Dr. James S. Wakeley, ERDC.

Karen C. Mulligan was the project proponent and coordinator at Headquarters, USACE. During the conduct of this work, Pat O’Brien was Chief of the Wetlands and Coastal Ecology Branch; Dr. Edmond Russo was

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Chief, Ecosystem Evaluation and Engineering Division; Sally Yost was Program Manager, WRAP; and Dr. Elizabeth Fleming was Director, EL.

COL Kevin J. Wilson was Commander of ERDC. Dr. Jeffery P. Holland was Director.

The correct citation for this document is:

U.S. Army Corps of Engineers. 2012. Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Hawai‘i and Pacific Islands Region Version 2.0, ed. J. F. Berkowitz, J. S. Wakeley, R. W. Lichvar, and C. V. Noble. ERDC/EL TR-12-5. Vicksburg, MS: U.S. Army Engineer Research and Development Center.

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1 Introduction

Purpose and use of this regional supplement

This document is one of a series of Regional Supplements to the Corps of Engineers Wetland Delineation Manual (hereafter called the Corps Manual). The Corps Manual provides technical guidance and procedures, from a national perspective, for identifying and delineating wetlands that may be subject to regulatory jurisdiction under Section 404 of the Clean Water Act (33 U.S.C. 1344) or Section 10 of the Rivers and Harbors Act (33 U.S.C. 403). According to the Corps Manual, identification of wetlands is based on a three-factor approach involving indicators of hydrophytic vegetation, hydric soil, and wetland hydrology. This Regional Supplement presents wetland indicators, delineation guidance, and other information that is specific to the Hawai‘i and Pacific Islands Region.

This Regional Supplement is part of a nationwide effort to address regional wetland characteristics and improve the accuracy and efficiency of wetland-delineation procedures. Regional differences in climate, geology, soils, hydrology, plant and animal communities, and other factors are important to the identification and functioning of wetlands. These differences cannot be considered adequately in a single national manual. The development of this supplement follows National Academy of Sciences recommendations to increase the regional sensitivity of wetland-delineation methods (National Research Council 1995). The intent of this supplement is to bring the Corps Manual up-to-date with current knowledge and practice in the region. The procedures given in the Corps Manual, in combination with wetland indicators and guidance provided in this supplement, can be used to identify wetlands for a number of purposes, including resource inventories, management plans, and regulatory programs. The determination that a wetland is subject to regulatory jurisdiction under Section 404 or Section 10 must be made independently of procedures described in this supplement.

This Regional Supplement is designed for use with the current version of the Corps Manual (Environmental Laboratory 1987) and all subsequent versions. Where differences in the two documents occur, this Regional Supplement takes precedence over the Corps Manual for applications in the Hawai‘i and Pacific Islands Region. Table 1 identifies specific sections of the Corps Manual that are replaced by this supplement. Other guidance

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Table 1. Sections of the Corps Manual replaced by this Regional Supplement for applications in the Hawai‘i and Pacific Islands Region.

Item

Replaced Portions of the Corps Manual (Environmental Laboratory 1987)

Replacement Guidance (this Supplement)

Hydrophytic Vegetation Indicators

Paragraph 35, all subparts, and all references to specific indicators in Part IV

Chapter 2

Hydric Soil Indicators Paragraphs 44 and 45, all subparts, and all references to specific indicators in Part IV

Chapter 3

Wetland Hydrology Indicators

Paragraph 49(b), all subparts, and all references to specific indicators in Part IV

Chapter 4

Growing Season Definition Glossary Chapter 4, Growing Season;

Glossary

Hydrology Standard for Highly Disturbed or Problematic Wetland Situations

Paragraph 48, including Table 5 and the accompanying User Note in the online version of the Manual

Chapter 5, Wetlands that Periodically Lack Indicators of Wetland Hydrology, Procedure item 3(g) and procedures given in this supplement and not listed in Table 1 are intended to augment the Corps Manual but not necessarily to replace it.

The Corps of Engineers has final authority over the use and interpretation of the Corps Manual and this supplement in the Hawai‘i and Pacific Islands Region.

Indicators and procedures given in this Supplement are designed to identify wetlands as defined jointly by the Corps of Engineers (33 CFR 328.3) and Environmental Protection Agency (40 CFR 230.3). Wetlands are a subset of the “waters of the United States” that may be subject to regulation under Section 404. One key feature of the definition of wetlands is that, under normal circumstances, they support “a prevalence of vegetation typically adapted for life in saturated soil conditions.” Many waters of the United States are unvegetated and thus are excluded from the Corps/EPA definition of wetlands, although they may still be subject to Clean Water Act regulation. Other potential waters of the United States in the Hawai‘i and Pacific Islands Region include, but are not limited to, tidal flats and shorelines along the coast and in estuaries; coral reefs; lakes; rivers; ponds;

anchialine pools; salt and mud flats; and perennial, intermittent, and ephemeral stream channels. Delineation of these waters is based on the high tide line, the “ordinary high water mark” (33 CFR 328.3e), or other criteria and is beyond the scope of this Regional Supplement.

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Amendments to this document will be issued periodically in response to new scientific information and user comments. Between published ver-sions, Headquarters, U.S. Army Corps of Engineers, may provide updates to this document and any other supplemental information used to make wetland determinations under Section 404 and Section 10. Wetland delin-eators should use the most recent approved versions of this document and supplemental information. See the Corps of Engineers Headquarters regu-latory web site for information and updates (http://www.usace.army.mil/CECW/

Pages/reg_supp.aspx). The Corps of Engineers has established an interagency National Advisory Team for Wetland Delineation whose role is to review new data and make recommendations for needed changes in wetland-delineation procedures to Headquarters, U.S. Army Corps of Engineers.

Items for consideration should include full documentation and supporting data and should be submitted to:

National Advisory Team for Wetland Delineation Regulatory Branch (Attn: CECW-CO) U.S. Army Corps of Engineers 441 G Street, N.W.

Washington, DC 20314-1000

Applicable region

This supplement is applicable to the Hawai‘i and Pacific Islands Region, which consists of the state of Hawai‘i, the Territory of Guam, the Commonwealth of the Northern Mariana Islands, and the Territory of American Samoa (Figure 1). The area includes Land Resource Region (LRR) V (Hawai‘i) and portions of LRR Q (Pacific Basin) recognized by the U.S. Department of Agriculture (USDA Natural Resources Conservation Service 2006). Most of the wetland indicators presented in this supplement are applicable throughout the entire Hawai‘i and Pacific Islands Region.

However, some indicators are restricted to specified subregions.

Physical and biological characteristics of the region

The Hawai‘i and Pacific Islands Region consists of island complexes scat-tered across the Pacific Ocean (Figure 1). The Northern Mariana Islands, Guam, and the Hawaiian archipelago are located in the northern Pacific Ocean, while American Samoa is located in the southern Pacific. These islands are separated by vast distances. The main islands of Hawai‘i are approximately 2,400 mi (3,900 km) southwest of the United States

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Figure 1. Location map of the Hawai‘i and Pacific Islands Region.

mainland. Guam (the southernmost of the Mariana island chain) is located an additional 3,800 mi (6,130 km) southwest of Hawai‘i. American Samoa is located 2,300 mi (3,710 km) southwest of Hawai‘i and 4,150 mi (6,695 km) from the U.S. mainland. Many of the islands are the exposed tops of partially submerged volcanic mountain ranges, although limestone terraces and coral atolls, built on the tops of submerged volcanic peaks, make up some islands. The region contains approximately 6,890 mi2 (17,840 km2) of land area and includes the major islands of the Hawaiian chain (Ni‘ihau, Kaua‘i, O‘ahu, Moloka‘i, Lāna‘i, Kaho‘olawe, Maui, and Hawai‘i), the Island of Guam, the Northern Mariana Islands (including Rota, Tinian, Aguijan, and Saipan), and American Samoa (including Ofu, Olosega, Ta‘u, and Tutuila) (Figure 2). Many smaller islands, some unin-habited, are also contained in the region. The Island of Hawai‘i, known as the Big Island, is the largest in the region and has the greatest topographic relief. The volcanoes of Mauna Loa and Mauna Kea dominate the island and rise to maximum elevations of 13,679 ft (4,169 m) and 13,796 ft (4,205 m) above sea level, respectively (Juvik and Juvik 1998; USDA Natural Resources Conservation Service 2006).

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Figure 2. Principal islands of the Hawai‘i and Pacific Islands Region.

Islands in the region lie within the Northeast or Southeast Trade Winds and have tropical to subtropical maritime climates, in which the average annual variations in air temperature are generally less than daily tempera-

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ture fluctuations (USDA Natural Resources Conservation Service 2006).

However, there is considerable spatial variability in both temperature and rainfall, especially on the higher islands that have greater topographic diversity and relief.

The variety of topographic, soil, and climatic conditions across the region, along with geographic isolation, has encouraged the development of a diverse Pacific flora with many species endemic to particular islands and island groups. The natural climax communities in the region range from high-elevation alpine and subalpine communities to wet, mesic, and dry hardwood forests, shrublands, grasslands, coastal strand, and coral atoll plant communities. Waves of human colonizers added large numbers of introduced and invasive plants to the flora, particularly in Hawai‘i. Early Polynesian settlers carried with them a number of important food plants, including taro (Colocasia esculenta), sweet potatoes (Ipomoea batatas), breadfruit (Artocarpus altilis), bananas (Musa acuminata), and yams (Dioscorea spp.) (Juvik and Juvik 1998). However, prior to the arrival of Europeans, most of the islands remained dominated largely by a complex and unique native flora. Settlement by Europeans (and, later, by Ameri-cans, Japanese, and others) led to large-scale agricultural development, primarily for sugarcane (Saccharum officinarum) production in the Hawaiian Islands and coconut oil and copra (Cocos nucifera) in American Samoa and the Marianas. Following World War II, lands in sugarcane production were converted to pastureland, secondary agro-forestry, and subsistence agriculture (Nakamura 1984; Young 1989; USDA Natural Resources Conservation Service 2006). Large-scale agriculture (e.g., for pineapple [Ananas comosus] and coffee [Coffea spp.]) remains prevalent in some areas, along with small commercial enterprises that grow food for local consumption. Many areas have become urbanized and industrialized with large areas utilized for tourism and military purposes.

The Hawaiian Islands

In the Hawaiian Islands, the average daily high temperature is about 84 °F (29 °C) and the average daily low temperature is 67 °F (19 °C) at sea level.

However, temperatures at high elevations regularly dip below freezing during the winter (Juvik and Juvik 1998). Average annual rainfall is about 70 in. (1,780 mm), but varies greatly by location in relation to north-easterly trade winds and topography. Annual rainfall ranges from about 10 to 60 in. (254 to 1,524 mm) on leeward slopes, and from 60 to more than 400 in. (1,524 to more than 10,160 mm) on windward slopes. The

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summit of Mt. Wai‘ale‘ale on the Island of Kaua‘i receives some of the highest rainfall totals on earth, with about 445 in. (11,300 mm) of precipitation per year. The islands have two seasons – a warm summer season with moderate rainfall from May through September and a cooler, rainy, winter season from October through April (Juvik and Juvik 1998;

USDA Natural Resources Conservation Service 2006). The amount of winter rainfall varies on a four- to seven-year cycle due to the El Niño Southern Oscillation (Juvik and Juvik 1998).

Soil parent materials on the main Hawaiian Islands consist of lava flows up to 5 million years old flanked by younger marine sediments and reef deposits (Juvik and Juvik 1998; Deenik and McClellan 2007). Carbonate sands, derived from weathered coral, shells, foraminifera, and coralline algae, are common in coastal areas. Each of the islands consists of one or more extinct volcanoes that have undergone significant erosion. Active volcanoes are present on the Big Island and Maui, although Maui’s Haleakalā volcano has not erupted since 1790 (Juvik and Juvik 1998).

Deeply incised valleys are common on most of the islands. Soils of the Hawaiian Islands are extremely diverse, with 10 of the 12 soil orders represented (Deenik and McClellan 2007).

The most common forest trees in the Hawaiian Islands are the native ‘ōhi‘a lehua (Metrosideros polymorpha) and koa (Acacia koa). More than 1,000 species of non-native and invasive plants have become established on the Hawaiian Islands. Common introduced trees include eucalyptus (Euca-lyptus spp.), common ironwood (Casuarina equisetifolia), rose apple (Syzygium jambos), albizia (Albizia spp.), and strawberry guava (Psidium cattleianum). Nearly 300 native Hawaiian plant species are listed as threatened or endangered under the U.S. Endangered Species Act, and another 50 are proposed for listing.

Guam and the Northern Mariana Islands

Seasonal northeasterly trade winds dominate the climate of Guam and the Northern Mariana Islands. Guam has a tropical maritime climate with air temperatures ranging from an average daily high of about 86 °F (30 °C) to an average daily low of 76 °F (24 °C). Average annual rainfall is about 86 in. (2,180 mm) and falls mainly during the rainy season from July through November (Young 1988; USDA Natural Resources Conservation Service 2006; U.S. Central Intelligence Agency [CIA] 2008). There is a moisture deficit (i.e., potential evapotranspiration typically exceeds pre-

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cipitation) from January to June (Young 1988). Occasional monsoonal storms and typhoons can produce very heavy rainfall. Annual rainfall totals are strongly influenced by the El Niño Southern Oscillation; during El Niño events, regional drought conditions may develop across the western Pacific. The Northern Mariana Islands have a similar climate with about two-thirds of the average annual rainfall occurring during the rainy season from July to November. Annual rainfall ranges from about 79 to 98 in. (200 to 250 cm) depending upon location, aspect, and elevation.

The average daily high temperature is about 86 °F (30 °C) and the average daily low temperature is about 68 °F (20 °C) (Young 1989).

The northern half of the island of Guam consists of a large limestone plateau of Eocene to Pleistocene age, bounded by cliffs (Carroll and Hathaway 1963; Tracey et al. 1964). The southern half of the island is a dissected, Quaternary-age, volcanic upland with interspersed limestone deposits. Fringing reefs surround most of the island (Tracey et al. 1964).

The soils of Guam are a diverse group of clays, silts, and sands developed on limestone and volcanic substrates (Carroll and Hathaway 1963). In the Northern Marianas, the islands of Saipan and Tinian are dominated by limestone plateaus of Pliocene and Pleistocene age. The volcanic core is exposed on about 10 percent of Saipan and less on Tinian (USDA Natural Resources Conservation Service 2006). Aguijan and Rota consist of con-centric limestone plateaus with steep escarpments and a volcanic core that is emerging in places (Young 1989).

Common trees of limestone areas on Guam include the native kafu‘ (Pandanus tectorius), pago (Hibiscus tiliaceus), mapunao (Aglaia mariannensis), paipai (Guamia mariannae), nonak (Hernandia sonora), fadang (Cycas micronesica), fagot (Neisosperma oppositifolia), gagu (Casuarina equisetifolia), and niyok (Cocos nucifera), and the introduced tangantangan (Leucaena leucocephala). On Saipan, in addition to the above, the native gulos (Cynometra ramiflora) and introduced sosugi (Acacia confusa) are also common. Volcanic substrates on Guam and the Northern Marianas support patches of native pago, kafu‘, puting (Barring-tonia racemosa), ladda (Morinda citrifolia), and ahgao (Premna obtusi-folia) in a largely fire-maintained savanna landscape dominated by grasses, such as Pennisetum polystachyon and Miscanthus floridulus (Young 1989; USDA Natural Resources Conservation Service 2006).

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American Samoa

American Samoa has a climate dominated by seasonal easterly and southeasterly trade winds, which produce a wet season from November to April. The territory receives abundant rainfall, averaging about 125 in.

(3,175 mm) at sea level and more than 200 in. (5,100 mm) at higher ele-vations (Nakamura 1984; USDA Natural Resources Conservation Service 2006; U.S. CIA 2008). The total land area of American Samoa is about 76 mi2 (197 km2). Tutuila, the largest island, has an area of 54 mi2 (140 km2) and its highest peak, Mount Matafao, rises 2,142 ft (653 m) above the waters of Pago Pago Bay. The remaining 22 mi2 (57 km2) include the three Manu‘a Islands of Ofu, Olosega, and Ta‘u, which has the highest peak in the territory, Lata Mountain, at 3,050 ft (930 m). Other islands in American Samoa include the islet of Aunu‘u near the eastern tip of Tutuila; Rose Atoll, 65 mi (105 km) east of the Manu‘as; and Swains Island, a small atoll located 200 mi (322 km) north of Pago Pago. The larger islands are characterized by steep volcanic mountainsides, small incised valleys, and a narrow coastal fringe. Soil characteristics vary widely between coastal fringes, mountains, and valleys (Nakamura 1984).

Most of American Samoa is forested with a variety of tropical hardwoods and palms. Common indigenous species include maota mea (Dysoxylum huntii), laga‘ali (Aglaia samoensis), mamalava (Planchonella samoensis), futu (Barringtonia asiatica), nui (Cocos nucifera), pu‘a (Hernandia nymphaeifolia), and fau (Hibiscus tiliaceus) (USDA Natural Resources Conservation Service 2006; Ragone and Lorence 2006).

Types and distribution of wetlands

The interplay of hydrology, salinity, and geomorphic setting determines the types and distribution of wetlands in Pacific island landscapes. Wetland water sources and flow regimes are varied and can be derived pre-dominantly from groundwater, surface water, or direct precipitation.

Groundwater and surface water can be saline or brackish in coastal areas, or influenced by fresh water from higher elevations, precipitation, or cloud drip. The tidal range in the Hawaiian Islands is about 3.3 ft (1 m) (Juvik and Juvik 1998) and is similar on other Pacific islands; this range limits the areas subject to regular tidal inundation. In addition to their hydrologic regimes, wetland types can be differentiated by vegetation type (often dominated today by non-native or invasive plant species) and substrate type, which may include bedrock (limestone or basalt), organic soils, or

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mineral soils (Erickson and Puttock 2006). The principal wetland types in the region are described briefly below.

Depressional wetlands occur on coastal plains behind beach or river berms, and in historic fish ponds that have filled with sediment. Their main water source is groundwater, which can be fresh in the wet season to hypersaline in the dry season and may be influenced by storm surges. In the main Hawaiian Islands, these wetlands typically are found on mudflats or in sandy areas, and support woody vegetation, such as saltwort (Batis maritima) and mangroves (Figure 3). In the Marianas and other Pacific islands, they can also be forested with Nypa palms, Barringtonia race-mosa, or other species. Examples of these wetlands can be found on the south shore of Moloka‘i, at Nukoli‘i on Kaua‘i, in the Kawainui Marsh and James Campbell National Wildlife Refuge on O‘ahu, and in the Kīhei wetlands on Maui.

Figure 3. Coastal wetland on Kaua‘i dominated by Batis maritima and mangroves.

Photo courtesy of the U.S. Fish and Wildlife Service.

Sloped marshlands or fern wetlands obtain their hydrology from shallow groundwater that may rise to the surface infrequently. They occur mainly in volcanic areas on slopes greater than 10 percent, particularly in the

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Mariana Islands. They typically have mineral soils and support mainly herbaceous vegetation (e.g., Nephrolepis ferns, Phragmites karka, and sedges), with scattered Pandanus tectorius trees. Examples include the Shell wetlands and Nimitz Hill marshlands on Guam and the upper Waipā Valley wetlands on Kaua‘i.

Hanging bogs occur in areas of abundant rainfall on steep volcanic slopes of 25 percent or more. Their hydrology is driven by groundwater perched over an aquitard of ironstone sheath. The soils are often organic (e.g., peats, mucks) and the vegetation is mainly herbaceous with stunted trees and shrubs (e.g., Metrosideros polymorpha). Examples can be found in the Waipā Valley of Kaua‘i and on high-elevation slopes in the Ko‘olau Mountains on O‘ahu.

Montane bogs are found mainly in volcanic areas that have flat to rolling topography, abundant precipitation (up to 445 in. [11,300 mm] per year), and a high water table and/or surface flow. They are found in the Alakai Swamp on Kaua‘i (Figure 4), on Mount Ka‘ala on O‘ahu, in the Kamakou Preserve on Moloka‘i, on Mount ‘Eke and Hāna Ranch on Maui, and in the Mauna Loa bogs on Hawai‘i. Montane bogs are dominated by native herbaceous, fern, shrub, and stunted forest species.

Forested wetlands are found at middle to higher elevations on all of the larger Hawaiian Islands with the exception of Kaho‘olawe and Ni‘ihau. They occupy slopes and depressions where the water table is often near the surface or where rainwater perches above a shallow aquitard or bedrock. In the Puna and South Hilo Districts on the Island of Hawai‘i, for example, many small wetlands exist in scattered depressions created by cracks, folds, and undulating flow patterns in pāhoehoe lava flows (Wakeley et al. 1996).

Riverine and open-water fringe wetlands are present throughout the region.

Their hydrology is derived mainly from the adjacent stream, lake, or pond.

They are generally fresh water but may be brackish to saline at their confluence with marine waters. The vegetation of fringe wetlands ranges from trees and shrubs (e.g., Rhizophora mangle, Xylocarpus moluccensis, and other mangroves; hau [Hibiscus tiliaceus]; and java plum [Syzygium cumini = Eugenia cumini]) to herbaceous plants (e.g., para grass [Urochloa mutica], sawgrass [Cladium mariscus ssp. jamaicense = C. jamaicense], and seashore paspalum [Paspalum vaginatum]). Throughout the region, this wetland type represents the greatest acreage of remaining low-elevation

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Figure 4. Aerial view of the Alakai Swamp, Kaua‘i, showing both forested and montane bog wetlands. Photo courtesy of the U.S. Fish and Wildlife Service.

wetlands. Hundreds of acres were used previously for the production of taro or rice (Oryza sativa); however, most wetland agriculture has now been phased out. Examples of riverine and open-water fringe wetlands can be found at Lake Susupe on Saipan, the Masefau Wetland on Tutuila, the lower Hanalei River on Kaua‘i, the Waipi‘o Valley on Hawai‘i, and Kawainui Marsh on O‘ahu.

Salt-flat and mud-flat wetlands are found along the immediate coastline and are subject to coastal overwash and spray. They have mineral sub-strates and vegetation often dominated by Batis maritima, Sporobolus virginicus, and sometimes kiawe (Prosopis pallida). Examples include those at Hanapēpē on Kaua‘i and Paikō Lagoon on O‘ahu.

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2 Hydrophytic Vegetation Indicators

Introduction

The Corps Manual defines hydrophytic vegetation as the community of macrophytes that occurs in areas where inundation or soil saturation is either permanent or of sufficient frequency and duration to influence plant occurrence. The manual uses a plant-community approach to evaluate vegetation. Hydrophytic vegetation decisions are based on the assemblage of plant species growing on a site, rather than the presence or absence of particular indicator species. Hydrophytic vegetation is present when the plant community is dominated by species that require or can tolerate prolonged inundation or soil saturation during the growing season.

Hydrophytic vegetation in the Hawai‘i and Pacific Islands Region is identified by using the indicators described in this chapter.

Many factors besides site wetness affect the composition of the plant community in an area, including regional climate, local weather patterns, topography, soils, natural and human-caused disturbances, and current and historical plant distributional patterns at various spatial scales. The insular floras of the Pacific basin are the result of development over different time spans and under influences from different source regions.

The native floras of the Hawaiian Islands and American Samoa, for example, differ substantially from that of the Marianas, including Guam (Mueller-Dombois and Fosberg 1998). The Hawaiian and Samoan Islands are within the Polynesian Region and are influenced by an Indo-Pacific flora with strong representation of American, New Zealand, and Antarctic components (Takhtajan 1986). The Mariana island chain is within the Micronesian Region and its flora is influenced by an Indo-Malaysian flora with strong connections to those of the Philippines, Indonesia, and Asia.

The flora of the Marianas lacks an American or boreal component. Unlike floras in some other parts of the Pacific basin, those of the Hawaiian Islands, Samoan Islands, and Marianas are composed mainly of species derived from plant colonists that took advantage of new habitats created by volcanic action. The regional floras of Polynesia and Micronesia historically were a mix of local endemics, Pacific regional endemics, and species associated with other nearby continental floras. All have suffered a heavy influx of invasive species resulting from human settlement, agri-culture, and urban development. Many wetlands in the region are

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dominated by hydrophytes that are not native to these islands. Today the wetland flora of the Hawaiian Islands includes about 1,400 taxa, while that of Guam and the Northern Mariana Islands includes approximately 800 taxa (U.S. Army Corps of Engineers 2009).

Hydrophytic vegetation decisions are based on the wetland indicator status (Reed [1988] or current approved list) of species that make up the plant community. Species in the facultative categories (FACW, FAC, and FACU) are recognized as occurring in both wetlands and uplands to vary-ing degrees. Although most wetlands are dominated mainly by species rated OBL, FACW, and FAC, some wetland communities may be domi-nated primarily by FACU species and cannot be identified by dominant species alone. In those cases, other indicators of hydrophytic vegetation must also be considered, particularly where indicators of hydric soils and wetland hydrology are present. This situation is not necessarily due to inaccurate wetland indicator ratings; rather, it is due to the broad toler-ances of certain plant species that allow them to be widely distributed across the moisture gradient.

Hydrophytic vegetation indicators and procedures presented in this chap-ter are designed to identify the majority of wetland plant communities in the region. However, some wetland communities may lack any of these indicators, at least at certain times. These situations are considered in Chapter 5 (Difficult Wetland Situations in the Hawai‘i and Pacific Islands Region).

Guidance on vegetation sampling and analysis

General guidance on sampling of vegetation for wetland-delineation pur-poses is given in the Corps Manual. Those procedures are intended to be flexible and may need to be modified for application in a given region or on a particular site. Vegetation sampling done as part of a wetland deline-ation is designed to characterize the site in question rapidly. A balance must be established between the need to accomplish the work quickly and the need to characterize the site’s heterogeneity accurately and at an appropriate scale. The following guidance on vegetation sampling is intended to supplement the Corps Manual for applications in the Hawai‘i and Pacific Islands Region.

The first step is to identify the major landscape units or vegetation com-munities on a site so they can be evaluated separately. This may be done in

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advance using an aerial photograph or topographic map, or by walking the site. In general, routine wetland determinations are based on visual esti-mates of percent cover of plant species that can be made either (1) within the vegetation community as a whole, or (2) within one or more sampling plots established in representative locations within each community.

Percent cover estimates are more accurate and repeatable if taken within a defined plot. This also facilitates field verification of another delineator’s work.

The appropriate size and shape for a sample plot depend on the type of vegetation (i.e., trees, shrubs, herbaceous plants, etc.) and the size or shape of the plant community or patch being sampled. The plot should be large enough to include adequate numbers of individuals in all strata, but small enough so that plant species or individuals can be separated and measured without duplication or omission, and the sampling can be done in a timely fashion (Cox 1990; Barbour et al. 1999). For hydrophytic vegetation determinations, the abundance of each species is determined by using areal cover estimates. Plot sizes should make visual sampling both accurate and efficient. The sizes and shapes of sampling plots, if used, may be modified as appropriate to adapt to site conditions and should be recorded on the field data form if they deviate from those recommended in the Corps Manual.

When sampling near a plant-community boundary, and particularly near the wetland boundary, it may be necessary to adjust plot size or shape to avoid overlapping the boundary and extending into an adjacent community having different vegetation, soils, or hydrologic conditions.

If it is not possible to locate one or a few plots in a way that adequately represents the vegetation unit being sampled, then percent cover estimates for each species can be made during a meandering survey of the broader community. If additional quantification of cover estimates is needed, then the optional procedure for point-intercept sampling along transects (see Appendix B) or other sampling procedures may be used to characterize the vegetation unit. To use the methods described in this paragraph, soil and hydrologic conditions must be relatively uniform across the sampled area.

Vegetation sampling guidance presented here and in the Corps Manual should be adequate for hydrophytic vegetation determinations in most situations. However, many variations in vegetation structure, diversity, and spatial arrangement exist on the landscape and cannot be addressed adequately in this supplement. A list of references is given in Table 2 for

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Table 2. Selected references to additional vegetation sampling approaches that could be used in…