CH Ecosystem Restoration 3 β Questions and Answers
Question 1: What hydrologic function does a floodplain reconnection project primarily restore?
- Tidal exchange with coastal waters
- Lateral hydrologic connectivity that attenuates floods and recharges groundwater (Correct answer)
- Longitudinal sediment continuity along the stream profile
- Vertical exchange between river and atmosphere
Correct answer: Lateral hydrologic connectivity that attenuates floods and recharges groundwater
Floodplain reconnection restores lateral connectivity, allowing flood waters to spread, slow, and infiltrate, reducing downstream peak flows and recharging alluvial aquifers.
Question 2: A Rosgen Level II survey classifies a reach as a C4 stream type. Which characteristic set defines this classification?
- Low sinuosity, steep gradient, cobble substrate
- High sinuosity, low gradient, gravel substrate, well-developed floodplain (Correct answer)
- Braided pattern, wide/depth ratio >40, sand bed
- Highly entrenched, moderate gradient, boulder substrate
Correct answer: High sinuosity, low gradient, gravel substrate, well-developed floodplain
Rosgen C streams are high-sinuosity, low-gradient channels with well-developed floodplains; the '4' suffix denotes a gravel-dominated substrate.
Question 3: Which remote sensing product is most useful for mapping pre-restoration tidal wetland extent to establish baseline conditions?
- MODIS 250 m NDVI composites
- Historical aerial photography and topographic charts combined with LiDAR DEMs (Correct answer)
- Synthetic aperture radar coherence maps alone
- Google Street View imagery
Correct answer: Historical aerial photography and topographic charts combined with LiDAR DEMs
Historical aerial photography and topo charts define pre-disturbance conditions, while LiDAR DEMs provide current elevation needed to model tidal inundation.
Question 4: In a tidal marsh restoration following dike removal, which process most rapidly re-establishes sediment accretion?
- Wind-driven aeolian deposition
- Tidal import of suspended sediment followed by organic matter accumulation (Correct answer)
- Riverine bedload transport
- Rainfall-driven sheet erosion from uplands
Correct answer: Tidal import of suspended sediment followed by organic matter accumulation
Tidal flows import suspended fine sediment that settles during slack water, and pioneer vegetation roots trap organics, driving rapid elevation gain.
Question 5: What is 'channel incision' and how does it impair ecosystem function in a restored stream?
- Lateral migration that widens the channel, reducing fish habitat
- Vertical downcutting that disconnects the stream from its floodplain and lowers the water table (Correct answer)
- Aggradation that buries spawning gravels with fine sediment
- Increased sinuosity that promotes bank erosion
Correct answer: Vertical downcutting that disconnects the stream from its floodplain and lowers the water table
Channel incision lowers the stream bed, disconnecting lateral floodplain access and dropping the riparian water table, degrading both aquatic and terrestrial habitat.
Question 6: Which biological indicator is commonly used to assess macroinvertebrate community response after stream restoration?
- Total phosphorus concentration
- Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxon richness (Correct answer)
- Chlorophyll-a biomass in the thalweg
- Dissolved oxygen measured only at night
Correct answer: Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxon richness
EPT richness is a widely used biotic index because these orders are sensitive to habitat and water quality degradation and recover with restoration.
Question 7: When conducting a sediment budget analysis for a restoration watershed, which term represents the net change in storage within the system?
- Sediment yield at the outlet only
- Inputs minus outputs plus or minus change in storage (Correct answer)
- Bedload transport rate alone
- Suspended sediment concentration at bankfull
Correct answer: Inputs minus outputs plus or minus change in storage
A sediment budget balances inputs, outputs, and storage change: ΞStorage = Inputs β Outputs, identifying sources, sinks, and transport linkages.
CH Ecosystem Restoration 3
What hydrologic function does a floodplain reconnection project primarily restore?