CH Conservation & Sustainability 2 — Questions and Answers
Question 1: Which hydrographic survey practice best minimizes disturbance to benthic habitat during nearshore surveys?
- Using multibeam sonar from a vessel with minimal draft (Correct answer)
- Deploying divers to manually measure depths
- Using single-beam sonar with frequent bottom contact
- Anchoring at multiple stations along the survey line
Correct answer: Using multibeam sonar from a vessel with minimal draft
Multibeam sonar from a shallow-draft vessel allows accurate nearshore mapping without physical contact with the seabed.
Question 2: What is the primary purpose of establishing minimum flow requirements (environmental flows) in a river system?
- To maximize hydropower generation
- To sustain aquatic ecosystems and downstream water users (Correct answer)
- To prevent sediment deposition in reservoirs
- To increase navigation channel depth
Correct answer: To sustain aquatic ecosystems and downstream water users
Environmental flow requirements define the minimum streamflow needed to maintain ecological function and support downstream users.
Question 3: A hydrographer discovers elevated turbidity downstream of a construction site. Which sustainable management action is most appropriate?
- Increase dredging to remove suspended sediment
- Notify regulatory authorities and recommend erosion controls at the source (Correct answer)
- Divert the river around the construction zone
- Install a dam to trap sediment
Correct answer: Notify regulatory authorities and recommend erosion controls at the source
Reporting to regulators and recommending source controls (silt fences, sediment basins) addresses the root cause rather than symptoms.
Question 4: Which metric is most commonly used to assess the long-term sustainability of a groundwater aquifer?
- Specific conductance of extracted water
- Ratio of annual recharge to annual extraction (Correct answer)
- Color and turbidity of well water
- Depth to confining layer
Correct answer: Ratio of annual recharge to annual extraction
Comparing annual recharge to extraction rates determines whether an aquifer is being used sustainably or depleted over time.
Question 5: What role does hydrographic data play in coastal resilience planning?
- It is used exclusively for commercial shipping route optimization
- It provides bathymetric and current data needed to model storm surge and flood risk (Correct answer)
- It determines property tax assessments in coastal zones
- It is used only for recreational boating safety
Correct answer: It provides bathymetric and current data needed to model storm surge and flood risk
Accurate bathymetric and hydrodynamic data underpin storm surge models, informing infrastructure and land-use decisions that build coastal resilience.
Question 6: Which approach best supports sustainable sediment management in a reservoir?
- Continuously increasing reservoir storage capacity
- Implementing sediment bypass tunnels or flushing operations (Correct answer)
- Removing all upstream vegetation to reduce inflow
- Lining the reservoir bed with impermeable material
Correct answer: Implementing sediment bypass tunnels or flushing operations
Sediment bypass tunnels and controlled flushing pass sediment through the reservoir, extending its lifespan and maintaining downstream sediment continuity.
Question 7: Under the U.S. Clean Water Act, what is the significance of defining the 'ordinary high water mark' in hydrographic surveys?
- It establishes the limit of federal navigational jurisdiction only
- It delineates the boundary of Waters of the U.S. for regulatory and wetland protection purposes (Correct answer)
- It sets the datum for chart datum adjustments
- It defines the area subject to commercial fishing permits
Correct answer: It delineates the boundary of Waters of the U.S. for regulatory and wetland protection purposes
The ordinary high water mark defines the lateral extent of Waters of the United States, triggering Clean Water Act protections for wetlands and water bodies.
CH Conservation & Sustainability 2
Which hydrographic survey practice best minimizes disturbance to benthic habitat during nearshore surveys?