PART I: ASSESSMENT OF WETLAND HYDROLOGY AT RESTORATION SITES PART II: CLIMATE CHANGE IMPACTS ON WETLAND HYDROLOGY BOUNDARIES Mike Vepraskas NC State
Do these sites have wetland hydrology? Restored and Created Wetlands
Overview Current status of wetland hydrology evaluation in NC Review a proposed wetland hydrology standard for restoration sites Review a test of the proposal
Who Oversees Wetland Restoration in NC? N.C. Ecosystem Enhancement Program (EEP) is a state agency that restores wetlands and waterways. EEP offers four mitigation programs to assist private and public groups comply with state and federal compensatory mitigation requirements for wetlands EEP can use fees to buy mitigation credits, or oversee new wetland restoration
Current Problems (Bad Press) The quality of the restoration efforts overseen by EEP varies. Wetland hydrology evaluation is difficult A new standard for hydrology is needed Developing a new standard became the job of the EEP s Science Advisory Panel
Evaluating Hydrology in Wetlands Wetland Hydrology determined by: Saturation occurring within a critical depth range during growing season. Minimum duration of saturation at critical depths met or exceeded Saturation occurs at required frequency Rainfall is normal or drier than normal
EEP Restoration Projects (Current Status) The NC EEP has: 114 reports online that contain data on hydrology and most have rainfall data Targeted durations of saturation for the wetland projects is between 5-25% of g.s. Rainfall data are generally reported, but were not used to evaluate hydrology in detail.
Overview Current status of wetland monitoring in NC Review proposed wetland hydrology standard Testing Protocol and Results
Proposed Hydrology Standard for EEP Adequate wetland hydrology in restored or reestablished wetlands: requires that the water table be within 30 cm of the surface, for a period of consecutive days that is >12.5% of the growing season. These requirements should be met following periods of normal rainfall, or drier than normal rainfall.
Duration and Growing Season The growing season is the frost free period based on the WETS data tables for a probability of 50% and an air temperature of 28 F. A duration of 12.5% was used as recommended by the Corps of Engineers. Areas saturated for shorter durations may or may not be wetlands.
Monitoring Period and Assessment Wetland hydrology will be monitored for 7 years as required by regulations. If the saturation depth and duration requirements are met for at least 4 out of the 7 years, then wetland hydrology will be considered to be met if rainfall is acceptable. Hydrology data should be assessed prior to the 7 year limit to detect potential problems developing at a site.
Overview Current status of wetland monitoring in NC Review proposed wetland hydrology criteria Testing Protocol and Results
Site Monitoring and Testing Wetland hydrology will be monitored with recording wells at every restoration site. Wells should extend to a depth of at least 1 m. Water table depths beneath the soil surface to be recorded at least once per day. Two or more measurements per day may be required if the data will be used to calibrate hydrologic models (DRAINMOD).
Juniper Bay Test Juniper Bay is a 750 ac. Carolina Bay in Robeson County, NC It was drained and farmed beginning in the 1970 s In 2005, it was restored to wetland for a NC DOT mitigation project. A consulting company was hired to evaluate the restoration.
Wetland Soils Map Organic soils Wettest Area Mineral soils Sandy rim Driest Area
Monitoring Well Locations 43 Wells Installed
Percentage of Wells Meeting Hydrology Standard Year Rainfall 2006 2007 2008 2009 2010 Wells Meeting Hydrology Requirement (%) Dry 29 88 77 37 0 Normal 45 0 7 40 49 Wet 0 0 0 7 0 Total 74 88 84 73 49
2006 Results Site Modification Needed Monitoring Well Locations (Failing)
Saturation Durations for Wells not Meeting Standard Year Duration 2006 2007 2008 2009 2010 days 0 to 6 3 1 1 1 3 7 to 13 4 1 1 2 2 14 to 20 0 3 5 1 9 21 to 28 4 0 0 3 8 Total Wells 11 5 7 7 22
Estimating Area Successfully Restored Year 2006 2007 2008 2009 Average Wells Meeting Standard (%) 74 88 84 73 80 Wetland Area Successfully Restored 80%
Summary The wetland hydrology standard is being tested. Testing uses existing site data from restoration sites. Additional modifications to the standard can be made should they be necessary. Early results show the standard is workable, but wetland boundaries may require shorter periods of saturation.
The End
PART II: CLIMATE CHANGE IMPACTS ON WETLAND HYDROLOGY BOUNDARIES M. J. Vepraskas, R.W. Skaggs, and C.P. Niewoehner NC State University
Will Climate Change Impacts be felt here?
Soils in 2013 Wetland Boundary Today Upland soils
Soils in 2070 Wetland Boundary Upland soils Edge of wetlands and soils suitable for septic
Jurisdictional Wetlands must have: Hydrophytic Plants Hydric Soils Wetland Hydrology (today s focus) Soils are saturated within 30 cm of the surface for 14 days or more during the growing season in 5 or more years out of 10.
Objectives 1. Estimate how predicted changes to rainfall and temperature through 2070 will affect the location of the wetland hydrology line in Eastern U.S.; 2. Estimate amounts of land area that may be affected if changes to the wetland hydrology line occur.
Methods 1. Sites 2. Wetlands 3. Hydrology Models 4. Climate Models
Daniels et al, 1999 Wet Flat Landscapes in the Coastal Plain Wet Flats
Water Budget of Wetland Used for Study Precip. Et Wetland Seepage
Climate Change Should affect Wetland Hydrology Boundaries Elevation (in.) 0 2 4 7 Wetland Boundary in 2070 Wetland Boundary in 2014 10 Wetland Bowl Wetland Bowl If wetland begins to dry up then the boundary should move downslope.
DRAINMOD was used to compute daily water table levels. Drain depth and distance adjusted to achieve target drainage rate Drainage rate Restrictive Layer
Ditch Depth and Spacing Adjusted until well was at the Wetland Hydrology Boundary Ditch Ditch 0 Slow Drainage Rate Restrictive Layer
7 d Wetland Hydrology Edge: 14 days Upland 15 d 20 d 30 d Wetland
METHODS Overview: a 4-Step Approach Calibrate model to predict Hydrology Line using climate data from 1983-2012 (current condition) Estimate amounts of land area affected Using predicted climate data in model for the new Hydrology Line for 2041-2070 Determine how the wetland hydrology line changes in elevation between time periods
Locations of Sites Evaluated Changes in Precip. (2070) Climatewizard.com
Wetland Hydrology Line Requirements Water Table Depth Period of Saturation Duration of Saturation Frequency 30 cm or 1 ft. Growing Season 14 d 50% of years
Climate Change Models Three models were obtained from the U.S. Forest Service. Measured rainfall from 1951 through 2000 were correlated with model predictions to identify the model giving the best fit.
Results 1. Impacts Across Eastern U.S. 2. Mapping Results for Pitt County, NC
Results from sites along Eastern U.S. Changes From 1983-2012 to 2041-2070 in: Sites Precip. Et % Temperature Portland Maine 5 32 12 Easton MD 8 18 8 Greenville NC -1 9 6 Miami FL -6 5 5
Predicting Climate Change Impacts on Wetland Boundaries in Eastern U.S. Elevation (in.) Florida Wetland Boundaries in 2070 Maryland NC Maine Wetland Boundary in 2014 0 2 4 7 10 Wetland Bowl Wetland Bowl
Results 1. Impacts Across Eastern U.S. 2. Mapping Results for Pitt County, NC
Results: A 30cm drop in the water table would result in a decrease in wetland area of 2% by 2041-2070. A drop of only 17 cm was predicted.
Conclusions The wetland hydrology line will move downhill as a result of global warming through 2070. Current wetland areas may shrink by <2% in NC. Wetlands will dry up earlier in the year due to increases in Et. Climate change impacts will be greater in northern U.S.
The End
Funding for this work has come from: For which we are thankful