# Presentation: 247768

## Using GIS to Conduct a Landscape Level Assessment of New Hampshire’s Wetlands

- Ted Walsh, Water Quality Specialist
- New Hampshire Department of Environmental Services
- Watershed Management Bureau

## Current Situation

- New Hampshire is in the process of rewriting our Comprehensive Monitoring Strategy
- Wetlands have previously not been addressed
- Little to no monitoring information
- Had no workable assessment units
- 2006 - No reporting in 305(b)

## Step 1 Creating Assessment Units and Buffers

## Overview

- National Wetlands Inventory (NWI) Polygons as a base
- Amalgamation of NWI Polygons into Assessment Units (AUs)
- Buffers on AU Amalgamations for Landscape Level Assessments

## Create workable and accurate AUID’s

## 83,565 NWI polygons statewide covering 484,845 acres

## Amalgamation of NWI Polygons into Assessment Units

- Trimmed out all Lacustrine/Limnetic, Palustrine/Open Water, Marine/Subtidal, Estuarine/Subtidal, and Riverine polygons
- Buffer all NWI polygons at 125m and merge all touching buffers so that those NWI polygons within 250m can be coded as within a single buffer complex
- Split any polygon bisected by a road
- Split any polygon bisected by a HUC12 divide.
- Assign unique AUIDs based upon HUC12 to the split buffer complexes
- Assign each AUID to one or more, full or partial NWI polygon as to maintain polygon level Cowardin Code

## NWI Buffered

## Assessment Units bisected by road split

## HUC 12 Divides

## Resulting AUID Buffer Complex Areas

## Resulting AUIDs (n=23,626) applied to NWI Polygons

## Cowardin Coding Maintained

##  Create Second Buffer Set for Landscape Level Assessments

- 125m buffer around all assessment units - donuts
- Ignored HUC 12 divides and road bisects used to create initial assessment units
- Buffer evaluated for factors other than just water quality

## Rebuffer Assessment Units

## Remove NWI Polygons from Buffers

**Notes:**
Wetland not used to evaluate self but could be used for nearby one.

## Step 2 Classification of Buffer Landcover Types 

## Evaluating the Buffers	

- Various datasets exist that classify landscape type.
- Propose to use National Landcover Data – Based on Landsat Thematic Mapper Imagery (30m resolution) – collected June 1999 through October 2003.
- Use GIS to tell us what % of each land cover class comprises a given buffer.

## NLCD Land Cover Class Definitions

| General Group | Code | Detailed Class |
| --- | --- | --- |
| Developed | 2 | High Intensity Developed |
| Developed | 3 | Medium Intensity Developed |
| Developed | 4 | Low Intensity Developed |
| Developed | 5 | Open Spaces Developed |
| Active agricultural land | 6 | Cultivated Land |
| Active agricultural land | 7 | Pasture/Hay |
| Active agricultural land | 8 | Grassland |
| Forested | 9 | Deciduous Forest |
| Forested | 10 | Evergreen Forest |
| Forested | 11 | Mixed Forest |
| Forested | 12 | Scrub/Shrub |
| Wetlands | 13 | Palustrine Forested Wetland |
| Wetlands | 14 | Palustrine Scrub/Shrub Wetland |
| Wetlands | 15 | Palustrine Emergent Wetland |

## NLCD Land Cover Class Definitions

**Developed, Medium Intensity** - Includes areas with a mixture of constructed materials and vegetation. Impervious surfaces account for 50-79 percent of the total cover. These areas most commonly include single-family housing units.
**Developed, High Intensity** - Includes highly developed areas where people reside or work in high numbers. Examples include apartment complexes, row houses and commercial/industrial. Impervious surfaces account for 80 to100 percent of the total cover.
**Cultivated Crops** - Areas used for the production of annual crops, such as corn, soybeans, vegetables, tobacco, and cotton, and also perennial woody crops such as orchards and vineyards. Crop vegetation accounts for greater than 20 percent of total vegetation. This class also includes all land being actively tilled.

## Pittsburg – Likely Low Impact 

## Pittsburg – Likely Low Impact

## Portsmouth – Likely High Impact

## Portsmouth – Likely High Impact

## Determine % of Each Landscape Type

- 40% Developed – Med. Density
- 20% Developed – Low Density
- 15% Pasture/Hay
- 10% Developed – High Intensity
- 5% Developed – Open Space
- 3% Palustrine – Scrub/Shrub
- 2% Estuarine – Emergent

- 60% Deciduous Forest
- 35% Mixed Forest
- 5% Pasture/Hay

_**Portsmouth**_

_**Pittsburg**_

## Step 3 Evaluation of Buffer Landcover Types

## Conduct a GIS Based Landscape Level Assessment of all Wetland Buffers

- Assess for “aquatic life” designated use
- Assessments to be based on an evaluation of the 125m buffers not the wetlands themselves (Donuts)
- No definitive support categories will be made due to the inherent roughness of this exercise.
- Use support categories
- 		-potentially supporting
- 		-potentially not supporting
- 		-insufficient information

## Weighting Impacts of Land Cover Classes

- Assign event mean concentrations for pollutants to NLCD land use coverages.
- Assign % impervious cover to each land use – a range of % impervious cover is given for each NLCD land cover class.
- For calculating pollutant loading use the highest value for each range.

## Event Mean Concentration Values (mg/L)

| Pollutant | Agriculture/
Pasture | Forest Rural Open | Highway | Industrial | Commer. |
| --- | --- | --- | --- | --- | --- |
| BOD (mg/L) | 5.5 | 3.0 | 17 | 15.3 | 14 |
| COD (mg/L) | 53 | 36.5 | 103 | 85 | 60.6 |
| TSS (mg/L) | 142.5 | 77.5 | 141.5 | 110.3 | 67.3 |
| TDS (mg/L) | 415 | 415 | 294 | 202 | 174 |
| TP (mg/L) | 0.705 | 0.12 | 0.39 | 0.24 | 0.23 |
| DP (mg/L) | 0.09 | 0.035 | 0.22 | 0.43 | 0.11 |
| TKN (mg/L) | 1.64 | 0.825 | 1.8 | 2.08 | 1.31 |
| NO2/3 (mg/L) | 4.06 | 0.67 | 0.83 | 1.5 | 0.81 |
| Pb (mg/L) |  | 0.27 | 0.17 | 0.28 | 0.068 |
| Cu (mg/L) |  |  | 0.04 | 0.076 | 0.049 |
| Zn (mg/L) |  | 0.142 | 0.21 | 0.502 | 0.18 |
| Cd (mg/L) |  |  | 0.003 | 0.005 | 0.003 |
| Fec. Coli | 3250 | 300 | 600 | 1022 | 4736 |

## Weighting Impacts of Land Cover Classes

- Assign event mean concentrations for each pollutant to NLCD land use coverages.
- Assign % impervious cover to each land use – a range of % impervious cover is given for each NLCD land cover class.
- For calculating pollutant loading use the highest value for each range.

## Impervious Fraction

| NLCD Landcover Type | % Impervious |
| --- | --- |
| High Intensity Developed | 100 |
| Medium Intensity Developed | 80 |
| Low Intensity Developed | 50 |
| Developed Open Space | 20 |
| Agriculture/Pasture | 15 |
| Forest/Rural/Open | 0 |
| Wetland/Water | 0 |

## Weighting Impacts of Land Cover Classes

|  | Forest  Rural Open | Water Wetland | Agricult.
Pasture | High Intensity Developed | Medium Intensity Developed | Low Intensity Developed | Developed Open Space |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Imper/Fraction | 0.00 | 0.00 | 0.15 | 1.00 | 0.79 | 0.49 | 0.20 |
| Load Ratio = (Annual Pollutant Load/Annual Pollutant Load for High Intensity) X 100 |  |  |  |  |  |  |  |
| BOD | 1 | 1 | 6 | 100 | 80 | 52 | 9 |
| CODTP | 2 | 1 | 12 | 100 | 80 | 52 | 12 |
| TSS | 4 | 1 | 27 | 100 | 80 | 52 | 20 |
| TDS | 11 | 0 | 40 | 100 | 80 | 52 | 49 |
| TP | 2 | 1 | 43 | 100 | 80 | 52 | 15 |
| DP | 1 | 1 | 7 | 100 | 80 | 52 | 7 |
| TKN | 2 | 2 | 16 | 100 | 80 | 52 | 16 |
| NO2/3 | 3 | 3 | 72 | 100 | 80 | 52 | 17 |
| Pb | 4 | 0 | 0 | 100 | 80 | 52 | 4 |
| Cu | 0 | 1 | 0 | 100 | 80 | 52 | 13 |
| Zn | 3 | 1 | 0 | 100 | 80 | 52 | 8 |
| Cd | 0 | 1 | 0 | 100 | 80 | 52 | 6 |
| Fecal Col | 0 | 0 | 14 | 100 | 80 | 52 | 17 |
| E. coli | 0 |  |  | 100 | 80 | 52 |  |
| Score | 3 | 1 | 18 | 100 | 80 | 52 | 15 |

**Notes:**
Final score is average

## Weighting Impacts of Land Cover Classes

|  | Forest  Rural Open | Water Wetland | Agricult Pasture | High Intensity Developed | Medium Intensity Developed | Low Intensity Developed | Developed Open Space |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Impervious Fraction | 
0.00 | 
0.00 | 
0.15 | 
1.00 | 
0.79 | 
0.49 | 
0.20 |
| Proposed Level 1 Wetland Assessment Score |  |  |  |  |  |  |  |
| Final
Score | 0 | 0 | 15.8 | 100 | 79.6 | 50.5 | 11.9 |
| Developed High Intensity Impact  100% Impervious Surface

At 10% Impervious Surface Water Quality Violations Likely
(Center for Watershed Protection/NHDES Coastal Impervious Surface Mapping) |  |  |  |  |  |  |  |
| Any wetland buffer with >10% Impervious Surface  Potentially Not Supporting |  |  |  |  |  |  |  |

## Calculating Level 1 Assessment Score

**Total *****Score =  ******Σ****** %******LC******i  * ****** LCS******i***
- where:
- Total Score = Total Assessment Score for Wetland Buffer
- %LC = percent of the total area in a given land cover class
- LCS = Assessment score for given land cover class
- Any score greater than 10  Potentially Not Supporting

**Notes:**
Weighting equation....weighting each score by its relative fraction in the buffer area.

## Sample Assessment - Pittsburg

| 
NLCD Landcover Class |  

Fraction | 
Land Cover Class Assessment Score | 

Total Score |
| --- | --- | --- | --- |
| 
Deciduous Forest
 | 
0.6 | 
0 | 
0 |
| 
Mixed Forest | 
0.35 | 
0 | 
0 |
| 
Pasture/Hay | 
0.05 | 
15.8 | 
0.79 |
| Potentially Supporting |  |  | 0.79  |

## Sample Assessment - Portsmouth

| NLCD Landcover Class |  Fraction | Land Cover Class Assessment Score | 
Total Score |
| --- | --- | --- | --- |
| Developed - Medium
 | 0.4 | 76.6 | 30.64 |
| Developed - Low | 0.2 | 50.5 | 10.1 |
| Pasture/Hay | 0.15 | 15.8 | 2.37 |
| Developed - High
 | 0.10 | 100 | 10.0 |
| Developed – Open Space | 0.05 | 11.9 | 0.60 |
| Palustrine – Scrub/Shrub | 0.06 | 0 | 0 |
| Estuarine - Emergent | 0.04 | 0 | 0 |
| Potentially Not Supporting |  |  | 53.61    |

## 

Contact Information:

Ted Walsh, Watershed Management Bureau
NH Department of Environmental Services
P.O. Box 95
Concord, NH 03302
(603) 271-2083
twalsh@des.state.nh.us

Additional Contributors:
Gregg Comstock
Ken Edwardson
Steve Gaughan

- Contact Information:
**Ted Walsh, Watershed Management Bureau**
**NH Department of Environmental Services**
**P.O. Box 95**
**Concord, NH 03302**
**(603) 271-2083**
- _[twalsh@des.state.nh.us](mailto:twalsh@des.state.nh.us)_
- Additional Contributors:
- Gregg Comstock
- Ken Edwardson
- Steve Gaughan

## Resulting AUIDs (n=23,626)

## Weighting Impacts of Land Cover Classes

- Based on event mean concentrations calculate estimated total pollutant load per year (lbs/yr) for each parameter
- Determine load ratio for each parameter and land cover class

- Load ratio = (Total Annual Pollutant Load/Total Annual Pollutant                Load for High Density) X 100
- e.g. 	Load ratio for Agriculture  34
- 	Load ratio for Low Density Developed  50

## Land Cover Class Weighted Scores

| General Group | Detailed Class | NHDES Wetlands Level 1 Assessment Score |
| --- | --- | --- |
| Developed | High Intensity Developed | 100 |
| Developed | Medium Intensity Developed | 79.6 |
| Developed | Low Intensity Developed | 50.5 |
| Developed | Open Space Developed | 11.9 |
| Agricultural Land | Cultivated Land | 15.8 |
| Agricultural Land | Pasture/Hay | 15.8 |
| Agricultural Land | Grassland | 11.9 |
| Forested | Deciduous Forest | 0 |
| Forested | Evergreen Forest | 0 |
| Forested | Mixed Forest | 0 |
| Forested | Shrub/Scrub | 0 |
| Wetlands | Palustrine/Forest Wetland | 0 |
| Wetlands | Palustrine Scrub Shrub Wetland | 0 |
| Wetlands | Palustrine Emergent Wetland | 0 |
| Wetlands | Estuarine Forested Wetland | 0 |
| Wetlands | Estuaruine Shrub/Scrub Wetland | 0 |
| Wetlands | Estuarine Emergent Wetland | 0 |
| Wetlands | Unconsolidated Shore | 0 |
| Barren Land | Snow/Ice | 0 |
| Water | Water | 0 |

## Weighting Impacts of Land Cover Classes

|  | Forest  Rural Open | Water Wetland | Agricult Pasture | High Intensity Developed | Medium Intensity Developed | Low Intensity Developed | Developed Open Space |
| --- | --- | --- | --- | --- | --- | --- | --- |
| Impervious Fraction | 0.00 | 0.00 | 0.15 | 1.00 | 0.79 | 0.49 | 0.20 |
| Proposed Level 1 Wetland Assessment Score |  |  |  |  |  |  |  |
|  | 0 | 0 | 15.8 | 100 | 79.6 | 50.5 | 11.9 |
| Developed High Intensity Impact  100% Impervious Surface

At 10% Impervious Surface Water Quality Violations Likely
(Center for Watershed Protection/NHDES Coastal Impervious Surface Mapping) |  |  |  |  |  |  |  |
| Any wetland buffer with >10% Impervious Surface  Potentially Not Supporting |  |  |  |  |  |  |  |
| Per Cent
Coverage to be PNS | 0 | 0 | 64 | 10 | 13 | 20 | 84 |