What are the goals of river management?
- flood control
- navigation
- recreation
- hydroelectric power generation
- water supply
- dams can accomplish all these functions *
How do we manage rivers?
Dams
Levees
Channel modifications
Diversion (aqueducts & pipes)
Land use (manage runoff)
Locks
What are run-of-the-river dams?
small dams; usually for power generation or water storage; most dams in NE U.S (no management of flow)
What are flood-detention dams?
bigger dams; reservoir is usually kept empty, only filled during major storm events (reservoir low compared to dam)
Multipurpose storage
big dams in the wester U.S.; water storage, plus power generation, flood control, and/or recreation
What are the two strategies for flood control?
- slow flow down (keep water in watershed)
- Land use
- Channel storage
- Dams - Methods that speed flow up (move water through channels faster)
- Levees
- Channel straightening, deepening, other modifications
The higher the peak discharge the worse ____________ there is
flooding
What is land use planning?
IDing flood-prone areas & setting zoning requirements to ensure damages are limited to area
What are some zoning requirements suggested by land use planning?
- avoid building residential areas in the floodplain
- protect building using pumps (if you do decide to construct)
- use floodplain land for parks, athletic fields, community gardens, forest buffers
What is a bio filtration swale?
detention area where water can flow in and be taken up by groundwater and plants
- harvests rainwater
Advantages of green roofs?
- Reduce stormwater runoff
- Reduce heating and cooling costs and energy usage
- Create habitats
- Improve air and water quality; reduce urban heat islands
Disadvantages of green roofs?
- Cost more than traditional roofs
- Require ongoing maintenance (even irrigation)
What happens when you take a meandering river and straighten it?
The river will wind up eroding its banks upstream and face deposition downstream
(if you straighten a river, must engineer the banks entirely)
Channelization (straighter)
water will flow fast
Channelization (smoother)
no concrete or vegetation
Channelization (deeper)
floodwalls and levees ensure water does not overflow onto floodplain
Channelization (trapezoidal)
minimize erosion
Pros of channelization and levee projects for flood control
- move more water quickly through channels (faster, deeper flow) = protects cities
- work well to protect infrastructure during high-frequency, low-magnitude floods
Cons of channelization and levee projects for flood control
- Levees fail catastrophically during big floods
- Flooplain cut off from channel, destroying habitats and losing temporary water storage on floodplains
- Increased erosion and deposition
- Faster transfer of flood peaks (spill over floodplain)
What kind of flood control method would be appropriate for a small stream in a city (i.e. Muddy River)?
Land use planning in the floodplain
What kind of flood control project would be appropriate for a large river flowing through a major city?
Channel straightening
Which kinds of flood control projects work by moving water through channels faster?
Levees & Channel straightening & concrete channels
Which of the following is a flood-control strategy that works by detaining water in the watershed?
using floodplains as parks
Tallest Dam in U.S
Oroville Dam, CA
