Two methods used to control annual floods were ______________
http://en.wikipedia.org/wiki/Flood_control
Two methods used to control annual floods are structural measures and non-structural measures.
1. Structural measures: These refer to physical modifications made to the natural environment to reduce flooding. Some common structural measures include:
- Construction of reservoirs and dams: These structures store excess water during periods of heavy rainfall and release it gradually, reducing the risk of downstream flooding.
- Levees and flood embankments: These are raised barriers constructed along riverbanks to contain water within the channel and prevent overflow onto surrounding areas.
- Channelization: This involves modifying the course of a river or stream by straightening its path, deepening the channel, or adding flood control structures to increase its capacity to carry water more efficiently.
- Flood control channels: These are specially designed waterways that divert excess water away from populated areas into designated drainage areas or storage reservoirs.
2. Non-structural measures: These involve policies, regulations, and actions that aim to minimize flood risks without altering the physical environment. Some examples include:
- Flood forecasting and warning systems: These systems use weather monitoring, river gauges, and predictive models to provide early warnings, enabling residents to evacuate and take protective measures in advance of a flood.
- Land-use planning and zoning: By regulating urban development and construction in flood-prone areas, communities can minimize exposure to flood risks. This may involve restrictions on building in low-lying areas or implementation of setback requirements from rivers or streams.
- Flood insurance: Encouraging residents and businesses in flood-prone areas to purchase flood insurance helps protect against financial losses in the event of a flood.
- Public awareness and education: Informing the public about flood risks, safety procedures, and the importance of taking preventative measures can increase preparedness and reduce vulnerability during floods.
- Emergency response planning: Developing comprehensive emergency response plans ensures that authorities and communities are prepared to respond effectively during a flood event, including evacuation procedures, temporary shelters, and mobilization of emergency resources.
These methods, whether structural or non-structural, can be used individually or in combination depending on the specific characteristics of the area and the nature of the flood risks being faced.
Two methods commonly used to control annual floods are:
1. Dams and Reservoirs: One method to control annual floods is by constructing dams and reservoirs. Dams are built across rivers to impound water, creating a reservoir. When excess water flows downstream during heavy rain or snowmelt, the dam can release water at a controlled rate, preventing flooding downstream. This controlled release helps to regulate the flow of water, reducing the impact of floods. Additionally, reservoirs can store excess water during periods of high rainfall, providing a buffer against floods.
To implement this method, engineers evaluate the local topography, hydrological data, and historical flood patterns to determine the ideal location and capacity of the dam and reservoir. Construction activities involve building a robust dam structure with spillways and outlets to control the water release. Environmental considerations are also taken into account to minimize adverse effects on ecosystems and habitats.
2. Channelization: Another method used to control annual floods is channelization. Channelization involves modifying or straightening rivers and streams to increase their capacity to carry water and reduce the chances of flooding. This method typically involves dredging, excavating, and reshaping the river channels to increase their flow capacity.
To implement this method, engineers perform hydraulic modeling studies to assess the river's current flow characteristics and identify areas prone to flooding. Based on these studies, they determine where and how the channel should be modified to enhance its flow capacity. Excavating equipment is then used to remove sediment, widen the channel, or redirect water flow. Additionally, stabilization measures such as lining the channel with erosion-resistant materials may be implemented to ensure the long-term effectiveness of channelization efforts.
It's important to note that both methods have their own set of advantages and limitations, and their implementation should be based on detailed engineering and environmental assessments specific to the location and river system in question.