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LAHAR & FLOOD CONTROL STRUCTURES

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Kristine Joyce Agustin

on 19 March 2014

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Transcript of LAHAR & FLOOD CONTROL STRUCTURES

A lahar is a type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris, and water. The material flows down from a volcano, typically along a river valley. Lahars are extremely destructive: they can flow tens of metres per second, be 140 metres (460 ft) deep, and destroy any structures in their path.
A flood is an overflow of water that submerges land which is usually dry. Flooding may occur as an overflow of water from water bodies, such as a river or lake, in which the water overtops or breaks levees, resulting in some of that water escaping its usual boundaries, or it may occur due to an accumulation of rainwater on saturated ground in an a real flood. While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, these changes in size are unlikely to be considered significant unless they flood property or drown domestic animals.
MT. PINATUBO ERUPTION
LAHAR
FLOOD
LAHAR & FLOOD CONTROL STRUCTURES
DAMS
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or prevent water flow into specific land regions.


CHECK DAM
These are small gravity dams, usually constructed with rocks and mortar or concrete, of variable height and width. These structures are located in small or medium-sized gullies to stabilize riverbed slopes and prevent soil erosion.
$1.25
Wednesday, March 19, 2014
Vol XCIII, No. 311
INTRODUCTION
LAHAR & FLOOD CONTROL STRUCTURES
LAHAR & FLOOD CONTROL STRUCTURES
RETAINING WALLS
These are rock/concrete block structures built on steep slopes anywhere in the watershed, where the erosion of the base foundation threatens lands and/or homes.

LAHAR & FLOOD CONTROL STRUCTURES
BUNDING
Bunding also called a bund wall, is a constructed retaining wall designed to prevent inundation or breaches from a known source. It is a secondary containment system commonly used to protect environments from spills where chemicals are stored.
LAHAR & FLOOD CONTROL STRUCTURES
Sausage Groynes
These are long, cylindrical, slightly flexible structures of variable thickness, composed of wire and rocks. Groynes are placed at the foot of banks along small, slow-moving streams, where there are signs of undermining and threats to permanent structures.

Sausage groynes are designed to stop such action by allowing the bank to collapse to an angle of repose in such a manner as to form a moderate slope, which encourages the growth of vegetation.

LAHAR & FLOOD CONTROL STRUCTURES
Gabion/Mattress Groynes

These are long, flexible structures of variable thickness, composed of wire and rocks. They are placed on the shaped banks of large, fast-moving streams where severe erosion is occurring and many pose a danger to permanent structures.

Mattress groynes are designed to prevent the further erosion of the riverbank. They trap soil particles to allow a build-up of soil; thereby encouraging the growth of vegetation.

LAHAR & FLOOD CONTROL STRUCTURES
PAVED DRAINS

These are concrete structures designed to quickly remove water from highly susceptible erodable areas such as road-sides, under-bridges and steep slopes.
LAHAR & FLOOD CONTROL STRUCTURES
LEVEES
These serve the purposed of confining flood waters to the stream and to portions of the flood plain. Levees are made of clay or earth fill material are being used with some structural modifications and have proven quite effective. The slopes of an earth fill levee should be no more than 2:1. The base should be wide to allow for a gradual slope. Trees and bushes should not be planted on or near a levee because their root systems tend to weaken it.
LAHAR & FLOOD CONTROL STRUCTURES
Flood Walls of reinforced concrete:

Flood walls require very little space and are often used to protect cities and developed areas. They are costly to construct, but involve minimal maintenance costs.

LAHAR & FLOOD CONTROL STRUCTURES
CHANNEL ALTERATION
Reduce floods by deepening and widening the channel by cutting meanders. Sometimes these works can have undesirable effects, by aiding the sediment transport process. Care must be taken when channel alternatives are considered.









DETENTION PONDS
Ponds placed on and off-side, can minimize the damage to downstream structures by reducing peak flows. They should be considered in the design of downstream protective structures.

AGUSTIN | CALMA | DIZON | QUIAMBAO | SUAREZ | TABINAS
PHOTO GALLERY :)
LAHAR
FLOOD WALL
LEVEE
FLOOD
CHECK DAM
MATTRESS GROYNE
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