CWD Field Survey & Data Collection 3 — Questions and Answers
Question 1: Which of the following is classified as a PRIMARY hydrology indicator under the Corps of Engineers wetland methodology?
- Drift deposits on vegetation
- Water marks on tree trunks
- Surface water present within or ponding the area (Correct answer)
- Oxidized rhizospheres along live roots
Correct answer: Surface water present within or ponding the area
Surface water present within or ponding the area is a primary hydrology indicator because it directly demonstrates inundation without requiring inference from secondary evidence.
Question 2: A wetland observation well (piezometer) installed at a survey site is used primarily to:
- Measure soil pH over time
- Monitor the depth and duration of seasonal water table fluctuations (Correct answer)
- Collect water samples for chemical pollutant analysis
- Mark the wetland boundary for GPS recording
Correct answer: Monitor the depth and duration of seasonal water table fluctuations
Observation wells record water table depth over time and are used to confirm whether hydrology criteria (saturation within 12 inches for ≥5–12.5% of the growing season) are met.
Question 3: During a field survey, 'oxidized rhizospheres' are best described as:
- Root channels packed with fibric organic debris
- Orange or reddish iron oxide coatings lining root channels in otherwise reduced soil (Correct answer)
- White salt crystalline deposits from evaporating groundwater
- Dense mats of fine roots at the soil surface
Correct answer: Orange or reddish iron oxide coatings lining root channels in otherwise reduced soil
Oxidized rhizospheres form when plants pump oxygen through their roots into anaerobic soil, causing localized iron oxidation that appears as orange or red coatings around root channels.
Question 4: In most temperate US regions, the optimal time to conduct a wetland hydrology field survey is:
- During the driest part of summer when hydrology indicators are most distinct
- During the growing season peak in July or August
- During the wet season (late winter/early spring) when indicators are most visible (Correct answer)
- Immediately after a major storm event regardless of season
Correct answer: During the wet season (late winter/early spring) when indicators are most visible
Late winter and early spring represent the peak hydrology period in temperate regions, when water table levels are highest and inundation/saturation indicators are most easily observed.
Question 5: 'Drift lines' as a secondary wetland hydrology indicator are best described as:
- Survey transect lines flagged parallel to drainage ditches
- Trails of fine sediment deposited by subsurface water movement
- Rows of dead plant material and debris deposited at the high-water mark as floodwaters recede (Correct answer)
- Lines of vegetation indicating old stream channel migration
Correct answer: Rows of dead plant material and debris deposited at the high-water mark as floodwaters recede
Drift lines are accumulations of organic debris, leaves, and fine sediment deposited in lines along vegetation or ground surface at the elevation reached by receding floodwaters.
Question 6: Under the three-parameter approach, wetland hydrology criteria are generally satisfied when the soil is saturated or inundated:
- At any depth for any duration during the calendar year
- Within 12 inches of the surface for a continuous or cumulative period equivalent to 5–12.5% of the growing season (Correct answer)
- At the surface continuously for more than 30 days per year
- Only when both saturation and surface inundation occur simultaneously
Correct answer: Within 12 inches of the surface for a continuous or cumulative period equivalent to 5–12.5% of the growing season
The Corps criteria require water within 12 inches of the surface for at least 5% (some supplements use up to 12.5%) of the growing season, which reflects the minimum duration needed to create wetland conditions.
Question 7: Which secondary hydrology indicator is typically most useful in a forested bottomland hardwood wetland?
- Algal mats or crusts on the soil surface
- Sediment deposits on aboveground surfaces of shrubs
- Water-stained leaves on the forest floor (Correct answer)
- Aquatic invertebrates observed in standing water
Correct answer: Water-stained leaves on the forest floor
Water-stained leaves accumulate on the forest floor and develop distinctive dark staining from prolonged inundation, making them a reliable secondary indicator in forested wetlands where other evidence may be seasonal.
CWD Field Survey & Data Collection 3
Which of the following is classified as a PRIMARY hydrology indicator under the Corps of Engineers wetland methodology?