watershed inventory and assessment module 7, part c – assessment

WATERSHEDINVENTORY AND

ASSESSMENT

Module 7, part C – Assessment

Developed by: Desotelle/Yoon Updated: Dec 2004 U3-m7c-s2

Watershed Inventory and Assessment

Assessment

Watershed

Condition

Evaluation

Monitoring

Plan

Issues and Description it’s about land use

Inventory Indicators that

measure watershed functions

Assessment (evaluation/monitoring)


Assessment Unit

Watershed components (functions, indicators, functional values)

Evaluation methods and examples Summarize inventory Choose evaluation method Evaluate the watershed Establish watershed goals


Watershed Components

Functions – characteristic of the watershed

Indicators – measures the function

Functional valuation – rating of the function

Peterson Environmental and Desotelle Consulting, 1997


Evaluation methods

Quantitative – ability to measure an indicator and apply it to a scientific range of numbers to evaluate a rating

Qualitative – rating methodology evaluated by an individual’s perception


Example

Example based on Carver County, Minnesota’s Wetland Inventory and Functional Value Analysis

Surface water runoff function Evaluates storage results for the attenuation of

peak high and low stream flows by the storage and slow release of water in the wetland


Stream Order

The stream/ditch order number connected to the wetland basin. High - 1st order or

no stream/ditch Moderate - 2nd or

3rd order Low - 4th order or

greater

Desotelle Consulting


Wetland Area/Watershed Area

The ratio of the wetland area to the subwatershed area High - >/= 0.02 Moderate - >/= 0.05

and <0.02 Low - <0.05



Gradient of Contributing Landscape

The greatest area covered by slopes ranging below from wetland to 800m out High - >/= 6% slope Moderate - >/=2%

and <6% slope Low - <2% slope



Runoff Final Landscape

Combined stream order, wetland area/watershed ratio, and gradient of contributing landscape High – stream order

high, or stream order moderate and other two are high

Moderate – All other combinations

Low – All low or any combination two lows and a moderate



Circular 39 Wetland Type

The predominant wetland type for the basin High - Types 3,

4, 5, 6, 7 Moderate -

Types 2 Low - Types 1,

90



Soil Hydrologic Group

The greatest area covered by soils types below from wetland to 800m out High - A, B soils Moderate - C, A/d,

B/d soils Low - D, C/d soils



Wetland Area

The area of the wetland basin High - >/= 5

acres Moderate - >/=

1and <5 acres Low - <1 acre



Runoff Final Wetland

Combined Circular 39 dominant type, soil hydrologic group, and wetland area High – All high or any

combination of two highs and a moderate

Moderate – All other combinations

Low – All low or any combination two lows and a moderate



Final Runoff Functional Value

Combining landscape and wetland functions for runoff into a final assessment High Both high Moderate All other combinations Low Both low or one low

and one moderateDesotelle Consulting


Wetland evaluation

Stormwater Function

Natural Resource Function

Lakes

Moderate - 1942Low - 1597

High - 54

County BoundaryWatershedsTransition areas

Null - 5

Transition areasWatershedsCounty Boundary

High - 935

Low - 2219Moderate - 434

Lakes

Null - 5

Transition areasWatershedsCounty Boundary

High - 935

Low - 2219Moderate - 434

Lakes



Oregon Watershed Assessment


Rapid Stream Assessment Technique

Inventory needs include Channel stability Channel scouring/sediment deposition Physical instream habitat Water quality Riparian habitat conditions Biological indicators (macroinvertebrates)

Relies on extensive field work Prioritize which streams need this work.


Rapid Stream Assessment Technique


Impervious Cover Model

Impervious cover <10% = sensitive

Impervious cover 10-25% = impacted

Impervious cover >25% = non-supporting

Photos Copyright 1999, Center for Watershed Protection


Select evaluation method(s)

There are many evaluation methods Research Select the methods the best fit information and

issues for your watershed


Summarize the inventory

Identify missing or unavailable information. Summarize information collected for each of

the manual components List issues that may require additional

assessment or data-gathering


Evaluate the watershed

Evaluate the functions of the aquatic–riparian system, fish populations, and water quality using the assessment technique(s) that best fit the watershed issues

Describe watershed areas and issues that should be the focus for action, including habitat restoration/protection opportunities.


References

Cowardin et al. Classification of Wetlands and Deepwater Habitats of the United States. 1979. FWS/OBS-79/31.

Shaw Samuel P. and Fredine C. Gordon. Wetlands of the United States. 1971. Circular 39. Fish and Wildlife Service.

Center for Watershed Protection. Rapid Watershed Planning Handbook. 1998. http://www.cwp.org.

EPA Surf your watershed http://www.epa.gov/surf Indiana Dept of Environmental Management, Office of Water Quality

http://www.in.gov/idem/water/planbr/wsm/iwpg/chap4.html Minnesota Forest Resources Council. Sustaining Minnesota Forest Resources:

Voluntary Site-Level Forest Management Guidelines for Landowners, Loggers, and Resource Managers. 1999. www.frc.state.mn.us

Oregon Watershed Assessment Manual http://www.oweb.state.or.us/publications/wa_manual99.shtml

Rosgen, Dave. Applied River Morphology. 1996. Wildland Hydrology, Pagosa springs, CO. Illustrations by Hilton Lee Silvey .

Snyder, Doug. A GIS Based Wetland Assessment Methodology for Urban Watershed Planning. 1997. Minnesota Board of Soil and Water Resources.

watershed inventory and assessment module 7, part c – assessment

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