New Hampshire Fluvial Geomorphology Assessments

Shane Csiki New Hampshire Geological Survey

New Hampshire Department of Environmental Services UMass Fluvial Geomorphology Workshop, Amherst

October 25, 2012

Assessment Objectives

• Fluvial Erosion Hazard (FEH) program • Geomorphic and aquatic organism passage

compatibility of stream crossings • Large woody debris jams for potential effects

of infrastructure • Site-specific assessments after flood events • Holistic understanding of river condition and

health • Integrated Watershed Management

FEH

FEH

FEH

• Emphasis on field photographs and use of GPS units to capture features

• Number of points on cross-sections

• Valley wall verifications • Option for more

detailed cross-section collection

Enhanced Large Woody Debris (LWD) Protocol

• Density of LWD • Qualification: - position in, or suspended

over bankfull width of channel

- Min L = 6 feet - Min D (wide) = 1 foot - Min D (6 feet from wide

end) = 0.5 foot

• GPS location • Root mats or

embeddedness in channel

L D

D

Enhanced Large Woody Debris (LWD) Protocol

• Volume of each piece – frustulum of a paraboloid

Culvert Assessments

Culvert Assessments NH Protocol – similar to Vermont, with

incorporated components from Mass.

Added For AOP – - Flow conditions (survey) - Depth/velocity in culvert

- Emphasis on

upstream/downstream/ reference bankfull widths - Crossing condition

Post-Flood Event Geomorphic Assessments

•Site visits in support of assessing flood and damage for determination of public safety risks

•Qualitative

•Examination of existing bed and bank condition and how it will impact flow, and determination of feedbacks upon bed/bank condition based upon new flow patterns

•Objective: Collation of photographs and assessment evaluation into reports provided to emergency response, stream permitting and funding assistance determinations