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Wetland Hydrology On-site Indicators Chapter 2

Wetland Hydrology On-site Indicators Chapter 2. COE Manual Criteria: Wetland Hydrology. No defined standard for wetland hydrology rule developed from pg 36,38,50 of manual and guidance letters “in most years” means at least 5 in 10 years or 50% probability in any one year

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Wetland Hydrology On-site Indicators Chapter 2

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  1. Wetland HydrologyOn-site IndicatorsChapter 2

  2. COE Manual Criteria: Wetland Hydrology • No defined standard for wetland hydrology • rule developed from pg 36,38,50 of manual and guidance letters • “in most years” means at least 5 in 10 years or 50% probability in any one year • 5% duration refers to a single, continuous episode of inundation or saturation (based upon BLH of SE) • depth of water table to meet “saturated to the surface” not defined in COE Manual. • Manual emphasizes the importance of saturation “within a major portion of the root zone”, usually within 12” of the surface

  3. WETLAND HYDROLOGY CRITERIA The hydrology criteria used by the USDA is defined by the National Food Security Act Manual (USDA, 1996). The definition is subject to change by lawmakers but at present is as follows: 1. Inundation (flooding or ponding) occurs for 7 consecutive days or longer during the growing season in most years (50% chance or more); or 2. Saturation at or near the surface occurs for 14 consecutive days or longer during the growing season in most years (50% chance or more). Soils may be considered to be saturated to the surface when the water table is within: a. 0.5 ft of the surface for coarse sand, sand, or fine sandy soils; or b. 1.0 ft of the surface for all other soils. Note: other definitions also apply, ex. FW, 15 days inundation

  4. FSA Manual Criteria • Provides a definite standard for wetland hydrology • Basically agrees with COE manual except for slight differences in time of duration • In both cases a water table within 12” of the surface would be taken to represent saturated conditions because of capillarity.

  5. By both manuals, hydrology criteria must be met during the growing season • Growing season is based upon the soil temperature regime.

  6. In the absence of soil temperature data, growing season can be approximated by air temperature • This represents the period between the last frost in spring and the first frost in fall • Data is available for every NRCS county office, also on Internet, a handout will have the address • WETS Table

  7. Hydrologic Inputs and Outputs • Wetlands continually gain and lose water • input may include direct precipitation, surface inflow, groundwater discharge • losses may include evaporation (from a water surface), transpiration (water loss through a plant), groundwater recharge, and surface outflow

  8. A water budget or water balance between the inputs and outputs describes the wetness of a site • this balance can change seasonallywith wet seasons and dry seasons • just as you checkbook describes your wealth and how it changes seasonally

  9. These are factors other than climate that affect hydrology • Landscape position: depressions, shorelines, flats, drainageways are generally the wettest parts of landscapes • shallow bedrock or slowly permeable soil horizons can perch water near the surface • fine textured soils drain more slowly and hold water longer than coarser soils • vegetation affects rate of water loss by transpiration, trees vs. herbaceous • How much can a tree transpire in a day?

  10. Geomorphic settings and water sources define familiar situations where we find wetlands • Ask what is the setting/landscape position here? • Ask what is the water source? • Ask what is the major water loss?

  11. Drainageways and floodplains are characterized by uni-directional flow and periodic flooding • Such as along a stream

  12. Variations in elevation and hydrology demonstrate the occurrence of wetlands in floodplains • low: abandoned river channels and backwater areas are often wettest • High: current and relic natural levees, when combined with their coarser materials - which drop out first, are often the driest areas on floodplains • natural levees typically require 10-yr flood to be inundated

  13. A rising and falling water table may result in a seasonal depressional wetland • The water table need not break the surface to produce a wetland. • Groundwater dominated systems are the most difficult for delineators to deal with

  14. Some depressional wetlands are due to perching of water above a slowly permeable soil layer. • Sites may be episaturated- perched water table above a restrictive horizon within 2m of surface • Soil profile must describe this restrictive layer

  15. Some wetlands are due to seasonal rising of a local groundwater. • Sites may be endosaturated- water table from local groundwater with a restrictive horizon greater than 2m from surface • Soil profile must show absence of a restrictive layer within 2m of surface

  16. Recorded Data

  17. Hydrologic Data considered recorded data- Stream and Lake gage data - Observation well data - Aerial Photography/Remote Sensing Data • Recorded data is the preferred data type • Data such as these can be used to determine whether a site meets wetland hydrology criteria directly • data should encompass the growing season or at least those portions that are wettest

  18. Gage data • Can be read directly • However, the tide gage and stream gage data must be related to site elevation • Interpolation between gages or the calculation of water surface profiles may be necessary • Water surface profiles are calculations of the water surface slope as you go upstream and downstream of a point-elevation change

  19. Observation well provides • Direct observation of water table • Wells for wetland determination should be shallow, < 2 feet, and be placed above any restrictive layer • Your manual contains a reference on the proper installation of wetland monitoring wells • Automatic recording wells can provide daily record, like gage data

  20. Gage/Well Data • Recorded data such as this provides a record of the timing and duration of saturation or inundation • Data like this is seldom available on a site due to time and expense constraints • Also gage data is often remote from the site in question, requiring additional evaluation to relate the data to the site.

  21. Aerial Photography • imagery must cover a sufficient span to meet frequency and duration criteria • Who has had an aerial photo interpretationcourse? • You must also have experience at photo interpretation

  22. COE has stream and lake data (elevations) • USGS has most stream data (discharge, need rating curve to establish elevation) • tide data is available from NOAA • NRCS WETS tables gives growing season • Additional data such as flood zones are available

  23. In the absence of recorded data, field indicators of hydrology are usedYour local COE District office is finalarbitrator of use and interpretationof on-site indicators of hydrology(I received my REGIV training from the Vicksburg, MS, COE District. Also taught that course later.)

  24. Inundation Saturation Water Marks Drift Lines Sediment Deposits Drainage Patterns Oxidized Root Channels Water-Stained Leaves Soil Survey (Data on Water Table) FAC-Neutral Test Other Field Indicators ofWetland Hydrology

  25. Field indicators of hydrologyPrimary Indicators • Primary indicators are those mentioned directly in the 87 manual • Any one establishes hydrology, but always record all that you find on site • Mark only those indicators you are willing to defend

  26. Field Indicators of hydrologySecondary Field Indicators • Secondary because they are only inferred in 87 manual • Established by March 92 COE Guidance Letter • Two or more required to meet hydrology criteria • Mark all that you find and are willing to defend(secondaries are intended for undisturbed sites)

  27. Hydrology Indicators on unaltered, non-manipulated sites - delineation could be done on vegetation and soils alone (all three criteria however must be met) - primary indicators should be evident, secondary indicators should be present - 87 Manual will give correct answers if applied properly - Field indicators of hydrology will not fail in this situation

  28. Hydrology Indicators on altered and/or manipulated sites - vegetation/soil may be disturbed, transitioning - primary indicators may not be evident, secondary indicators may not be present and were not meant for this situation (ex. FAC Neutral test doesn’t make a lot of sense, Soil Survey is for undrained condition) - Field indicators of hydrology may not provide a definitive answer - Situation: Agricultural field

  29. EXPLANATION OF INDICATORS - Field Indicators are Positive Indicators Only - presence of indicator means presence of hydrology - lack of indicator does not mean lack of hydrology - While the three wetland criteria must be established independently, the preponderance of evidence must be used in making wetland determinations - Secondary Indicators should be cautiously applied to altered and/or manipulated sites

  30. Primary Indicator:Visual Observation of Inundation A Condition in Which Water From Any Source Temporarily Or Permanently Covers A Land Surface May be from: - Ponding - Flooding Record depth of inundation

  31. INUNDATION: a condition in which water from any source temporarily or permanently covers the surface.

  32. Primary Indicator: InundationType: Ponded A Condition In Which Water Stands In A Closed Depression. The Water Is Removed Only By Percolation, Evaporation, Or Transpiration Record depth of ponding

  33. PONDING: a condition in which water stands in a closed depression. Water removed by: ET or percolation only.

  34. Primary Indicator: InundationType: Flooded The Soil Surface Is Temporarily Covered With Flowing Water from Any Source, Such As Overflowing Streams Or Rivers, Runoff From Adjacent Slopes, And Inflow From High Tides Record depth of flooding

  35. FLOODING PONDING FLOODING: the soil surface is temporarily covered by flowing water from any source: river, uplands, tides.

  36. Primary Indicator:Visual Observation of Saturation A Condition In Which All Easily Drained Pores Between Soil Particles Are Temporarily Or Permanently Filled With Water • The soil can become saturated either from above (episaturation, due to perched water table) or below (endosaturation, due to groundwater, no restrictive layer within 2 m of the soil surface)

  37. SATURATION: a condition in which all easily drained pores between soil particles are filled with water, temporarily or permanently. Vegetation indication, no visible water.

  38. Primary Indicator: SaturationPresence of Water Table The Level At Which Water Stands In An Unlined Bore Hole Record depth to free water surface

  39. SATURATION LEVEL Water Table WATER TABLE: the level at which water stands in an unlined bore hole. NRCS uses water table. COE can use saturation level (capillary rise).

  40. Capillary Fringe A Zone Immediately Above The Water Table In Which Water Is Drawn Upward By Capillary Action - For COE, consider effect of capillary fringe on zone of saturation (ex. Water table at 14”, saturated at 11”, indicator) - For FSA, consider position of water table only (ex. Water table at 14”, no indicator)

  41. CAPILLARY FRINGE: a zone immediately above the water table in which water is drawn upward by capillary action.

  42. Primary Indicator: Water Marks Water marks are created by the staining effect of sustained water elevation on trees and other fixed objects. Will appear as a distinct line created on fixed objects, including vegetation. DO NOT confuse with elevated lichen lines and upper extent of bryophyte growth- should be on several objects at same elev.- should be able to cover upper line with a brass ring - Record location, height, photograph

  43. WATER MARKS: staining on trees and other fixed objects due to prolonged exposure to water. Note: lower limit of lichen and upper limit of bryophytes is not the same as a water mark, although a trained individual may use them to establish water elevation. Low frequency event, 10-yr flood High frequency event, 2-yr flood

  44. Primary Indicator:Drift Lines Deposition Of Debris Typically Found Adjacent to Streams or Other Water Flow in Wetlands Can occur in depressions Record description, photograph, elevation

  45. DRIFT LINES: debris that normally marks the highest elevation of an event.

  46. DRIFT LINE DRIFT LINES: debris that normally marks the highest elevation of an event. Along streams debris may be in trees.

  47. Primary Indicator:Sediment Deposits - Deposits of sediment from flowing water on the wetland soil surface, leaf litter, or plants when the water is slowed - typically found in backwater and slackwater areas Record description, location, photograph

  48. SEDIMENT DEPOSITS: leaves have sediment deposits on them indicating water transport of sediment, inundation - flooding.

  49. SEDIMENT DEPOSITS: upward face of leaves have sediment deposits on them. Pick up leaves turn them over.

  50. Primary Indicator:Drainage Patterns - Along Floodplains Where Overbank Flooding Erodes Sediments. - Possible Absence of Leaf Litter From the Soil Surface Note: for use with flooding type inundation Record description, photograph

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