Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

How to estimate future forest cover in a watershed

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

“Watershed forestry is the use of forests and the practice of forestry to protect, restore, and sustain water quality, water flows, and the health and function of watersheds.” (WFAP federal

register)

“Urban Watershed Forestry”

“Urban is ….well….urban - developed and developing areas”

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

reduce stormwater runoff improve air quality reduce stream channel

erosion provide habitat for

terrestrial and aquatic wildlife

improve soil and water quality

reduce summer air and water temperatures

Watershed Benefits of Forest Cover

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Link Between Forest Cover and Stream Health

• Stream health rating of Excellent requires no more than 6% IC and at least 65% riparian forest cover (Goetz et al, 2003)

• Stream health rating of Good requires no more than 10% IC and at least 60% riparian forest cover (Goetz et al, 2003)

• Watersheds with at least 65% forest cover usually had a healthy aquatic insect community (Booth, 2000)

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Urban Watershed Forestry Goals and Objectives:

Protect Protect priority forests Prevent forest loss during

development and redevelopment Maintain existing forest canopy

Enhance Enhance forest fragments

Reforest Plant trees during development and

redevelopment Reforest public land Reforest private land

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Urban Watershed Forestry Manual Series

part 1: Methods for Conserving forest cover in a watershed

part 2: Conserving & Planting Trees at Development Sites

part 3: Urban Tree Planting Guide www.forestsforwatersheds.org

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Planning Methods for Increasing Forest Cover in a Watershed

Step 1. Conduct a Watershed Leaf-Out Analysis

Step 2. Develop forest cover goals and objectives for the watershed

Step 3. Identify existing forest and reforestation opportunities

Step 4. Conduct a field assessment of existing forest and reforestation opportunities

Step 5. Prioritize existing forest and reforestation opportunities

Step 6. Develop recommendations for meeting forest cover goals

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

The Leafout Analysis

• GIS-based method to estimate future forest cover in a watershed

• Local governments /watershed groups can use method to:• evaluate the effect of different watershed protection

scenarios on future forest cover• set numeric forest cover goals• develop watershed protection recommendations

• Leafout Analysis spreadsheet available at: www.forestsforwatersheds.org

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

GIS data needs for Leafout Analysis

• Watershed boundary• Property boundaries and parcel data• Hydrology and roads• Current forest cover• Zoning• Protected parcels– conservation easements,

conservation or parkland zoning• Land cover coefficients• Recent aerial photos may also be helpful

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Leafout Analysis Assumptions

• Full buildout of the watershed will occur based on allowable zoning (e.g., no rezoning)

• Current forest cover on developed land, protected lands (and agricultural lands with future agricultural zoning) will remain the same with the future buildout

• Future forest cover on buildable land can be predicted by using forest cover coefficients

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Leafout Analysis Caveats

• Intended for use as a planning exercise, not a precise predictor of future forest cover.

• Does not account for tree removal or mortality (other than that related to land development)

• Default values are provided but use local data where available

• Measures forest cover not urban tree canopy

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Forest cover vs. tree canopy

Graphic source: Goetz et al 2003

Forest cover: area of land that is classified as forest.

Tree canopy: layer of leaves, branches and stems that cover the ground when viewed from above.

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Leafout Analysis Steps

1. Calculate current forest cover in the watershed2. Identify buildable and unbuildable parcels3. Calculate the area of each zoning category for

buildable land 4. Multiply buildable land in each zoning category by

the corresponding forest cover coefficients5. Calculate current forest cover on unbuildable land6. Sum future forest cover on buildable and

unbuildable land

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Step 1: Calculate Current Forest Cover

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

No buildings. Parcels not

selected

Parcels intersect with buildings so they are selected

as “developed” parcels

Step 2: identify buildable and unbuildable parcels

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Step 2: other parcels to consider “unbuildable”

• Parcels that are permanently protected from development by easement or other conservation measure (e.g., conservation zoning)

• Lands currently in agricultural use that also have future Agricultural zoning

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Step 2: resultsWatershed boundary

Unbuildable land

Buildable land

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Step 3: calculate the area of each zoning category for

buildable land

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Step 3: additional data requirements

• Calculate current forest cover on:• Buildable very low density residential (e.g., x

du/acre), open urban, and agricultural lands

• Why?• Forest cover on VLDR and Open Urban land varies

based on pre-development forest cover• Assumption that most agricultural lands will keep

existing forest if zoned agricultural in the future

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Step 4: multiply the buildable land in each zoning category by the corresponding forest cover

coefficients• Forest cover coefficients represent the

fraction of a particular land use that is covered by forest

• Forest cover coefficients vary by land use and potential natural vegetation (and by pre-development forest cover for some land use types)

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Forest Cover CoefficientsLand Use Description Forest Cover

Coefficient

Low density residential 1-4 dwelling units (DU) per acre

0.034

Medium density residential

5-10 DU/acre 0.033

High density residential > 10 DU/acre 0.028

Commercial Retail, small office, businesses

0.010

Industrial Manufacturing and industrial facilities, including warehouses, office parks

0.005

Institutional Schools, churches, government offices and facilities

0.022

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Predicting Future Forest Cover on Very Low Density Residential

and Open Urban Land

Land Use Description Equation to Predict Future Forest Cover (%)

Very low density residential

< 1 DU/acre Y = 0.71x + 3.97, where:Y = post-development forest cover %x = pre-development forest cover %

Open urban land golf courses, parks, recreation areas

Y = 0.87x + 1.42, where:Y = post-development forest cover %x = pre-development forest cover %

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Step 4: ResultsLand Use Buildable

AcresForest Cover Coefficient

Future Forest Cover (Acres)

Low density residential 320 0.034 10.88

Medium density residential 5,600 0.033 184.80

High density residential 232 0.028 6.50

Commercial 99 0.010 0.99

Industrial 34 0.005 0.17

Institutional 23 0.022 0.51

Open urban 47 0.358 16.83

Very low density residential

28 0.461 12.92

Total 6,383 N/A 233.60

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Step 5: calculate current forest cover on unbuildable land

Step 6: sum future forest cover on buildable and unbuildable land

Current forest cover on unbuildable land: 639 acres

Future forest cover on buildable land (estimated using land cover coefficients): 600 acres

+

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Leafout Analysis SpreadsheetCompiles result of the Leafout steps

• Input watershed data

Leafout Analysis Spreadsheet1. Fill in the requested values in the Input Watershed Data tab (these are

derived from GIS analysis)

2. Go to the See Future Forest Cover Results tab to view the estimated future forest cover and % loss

3. Set an initial forest cover goal and select from four urban watershed forestry practices in the Select Management Practices tab

4. Go to the Re-Evaluate Future Forest Cover tab to see the effect of the selected practices on future forest cover

5. Revisit the Select Management Practices tab and make changes if desired

6. Use the Finalize Management Practices tab to summarize your final forest cover goal, management practices and timeframe for implementation

Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry Center for Watershed Protection USDA Forest Service, Northeastern Area, State and Private Forestry

Urban Watershed Forestry Practices

• Options in the Leafout Spreadsheet:• Conserve forest on individual parcels through

purchase /easement• Adopt a local forest conservation ordinance for new

development• Implement reforestation projects on public lands• Initiate an outreach/incentive program focuses on tree

planting for private landowners

• A complete list of urban watershed forestry practices in available in the manual series