CFS CFS Environmental & Ecological Considerations 2 — Questions and Answers
Question 1: What is the primary goal of floodplain restoration as a flood mitigation strategy, compared to structural approaches like levees?
- To increase the flood zone designation of adjacent properties
- To reconnect rivers with their natural floodplains and restore natural storage capacity (Correct answer)
- To permanently dewater wetlands for agricultural use
- To accelerate sediment transport downstream
Correct answer: To reconnect rivers with their natural floodplains and restore natural storage capacity
Floodplain restoration reconnects rivers to their natural floodplains, restoring the natural flood attenuation, water quality, and ecological functions that development and channelization have diminished.
Question 2: Under the Endangered Species Act, what obligation does a federal agency have if a proposed floodplain project may affect a listed species?
- Pay a mitigation fee and proceed
- Consult with the U.S. Fish and Wildlife Service or NOAA Fisheries under Section 7 (Correct answer)
- Relocate the species before construction begins
- Obtain a Section 404 permit instead
Correct answer: Consult with the U.S. Fish and Wildlife Service or NOAA Fisheries under Section 7
Section 7 of the Endangered Species Act requires federal agencies to consult with USFWS or NOAA Fisheries to ensure federally funded or permitted actions are not likely to jeopardize listed species or destroy critical habitat.
Question 3: Which term describes the gradual loss of land at a stream bank due to water erosion, a process relevant to floodplain boundary delineation?
- Aggradation
- Avulsion
- Lateral erosion (bank erosion) (Correct answer)
- Subsidence
Correct answer: Lateral erosion (bank erosion)
Lateral erosion or bank erosion is the gradual wearing away of streambanks by flowing water, which can shift channel position and alter the boundaries of the mapped floodplain over time.
Question 4: Green infrastructure approaches in floodplain management include which of the following?
- Concrete channel lining
- Detention basins, bioswales, and urban tree canopy expansion (Correct answer)
- Levee construction and channel dredging
- Culvert upsizing to increase flow velocity
Correct answer: Detention basins, bioswales, and urban tree canopy expansion
Green infrastructure uses natural and nature-based features such as bioswales, rain gardens, permeable pavement, and restored floodplains to manage stormwater and reduce flood risk.
Question 5: What is 'natural channel design' in floodplain and stream management?
- Lining channels with concrete to maximize flow capacity
- Engineering channels to mimic natural stream geometry, pattern, and profile (Correct answer)
- Straightening meandering streams to reduce flood extents
- Installing gabion walls along all channel banks
Correct answer: Engineering channels to mimic natural stream geometry, pattern, and profile
Natural channel design (also called stream naturalization or geomorphic channel design) restores stream channels to stable, natural forms that balance sediment supply, flow, and ecological function.
Question 6: Which ecological concept describes the maximum volume of water a natural floodplain-river system can store or convey without exceeding flood stage, important for floodplain capacity analysis?
- Flood frequency
- Hydraulic conveyance and floodplain storage capacity (Correct answer)
- Drainage density
- Runoff coefficient
Correct answer: Hydraulic conveyance and floodplain storage capacity
Hydraulic conveyance and floodplain storage capacity describe the combined ability of the channel and adjacent floodplain to carry and temporarily hold floodwater without exceeding bankfull or flood stage.
CFS CFS Environmental & Ecological Considerations 2
What is the primary goal of floodplain restoration as a flood mitigation strategy, compared to structural approaches like levees?