FLOOD MIDTERM EXAM

Flood

overflow of water that submerges land that is usually dry

Flood

most common and widespread natural severe weather event

River Flood

when water levels rise over the top of riverbanks

Sudden River Flooding

occur more often on smaller rivers

Low-rising River Floods

occur in large rivers with large catchment area

Catchment Area

where precipitation collects and runs off into a common outlet

Coastal Flood

inundation of normally dry land areas along coast with seawater

Storm Surge

abnormal rise in water level in coastal area

Storm Surge

result of storms that cause higher than normal tides on coast

Storm Surge

most dangerous aspect of any tropical system, most threat to both life and property

Urban Flooding

Inland Flooding is also called

Flash Flood

this is also a type of inland flooding

Inland / Urban Flooding

occurs inland or not in coastal

rainfall

this is usually to blame for inland floods

snowmelt and blocked waterways

other than rainfall, these 2 also cause inland / urban flooding

urban

Inland floods are often worse in ___ areas

Flash Flood

the most well-known and deadly type of flood because they are extremely powerful

Flash Flood

can wipe out everything in their paths

Flash Flood

can happen little to no warning

River Flood, Coastal Flood, Storm Surge, Urban Flooding, and Flash Flood

5 type of flood

Channels with Steep Sides

flooding occurs when there is fast runoff into lakes, rivers, and other reservoirs

Direct Loss

type of loss during flood

Indirect Loss

type of loss after flood

Monetary / Tangible

type of loss from flood where the item can be sold/bought

Non-monetary / Intangible

type of loss from flood where the item can't be sold/bought

death (loss of lives)

gravest effect of flooding

Mitigation

sustained action taken to reduce or eliminate long-term risks to people and property from hazards

Structural Mitigation Measures

alter characteristic of flood, and reduce probability of flooding

Nonstructural Mitigation Measures

does not alter characteristics of flood, but reduce consequences of flooding

Levees, floodwalls, seawalls, and other appurtenant structures

prevent floodwaters and storm surges from reaching areas that are at risk, so floodwaters rise gradually

Dams

barriers that impound hydrologic flows, retain floodwaters before they reach areas at risk

Floodways, spillways, and channels

carry floodwaters around a community

Controlled Overtopping of Levees

design of levee to force overtopping in the least hazardous location

superiority or notches or openings

different levee heights known as

Controlled Breaching of Levees

rare, only when benefit of this is justified economically; last ditch to lower flood threatening high-value area

Forced Breaches

routinely during floods to drain flooded land if no other means of draining or when diked tract of land is compromised by flooding

Levee Armoring

making levee less susceptible to erosion by floodwaters and overtopping

concrete to vegetation

levee armoring uses materials from ___ to ___

Cutoff Walls and Trenches

stop the flow through and below a levee

Land-side seepage berms

add sufficient weight to counteract the upward seepage forces

Pressure relief wells

on the land side of the levee to deal with seepage

Structure Elevation

raising a structure above the expected flood level, flood damages can be prevented

Base Flood Elevation

BFE

Natural Systems

store overflow waters from river line flooding and help reduce downstream impacts / reduce flooding behind levees with interior drainage problems

Wetlands

natural barrier to storm surge inundation

Coastal Sand Dunes

protect structures behind them and help slow down coastal erosion and also the immediate impact of rising storm surge

Floodways

a natural system that relieve flood pressure can also provide ecosystem benefits

Risk Mapping

Hazard Forecasting, Early Warning Systems, and Emergency Plans

#3 and #4 sa Nonstructural Mitigation Measures

Dry and Wet Floodproofing

combination of adjustments and additions of features to buildings that eliminate or reduce the potential for flood damage

Dry Floodproofing

seals structures to prevent floodwaters from entering

Wet Floodproofing

makes uninhabited portion of a structure resistant to floods by allowing water to enter and flow through the structure during a flood

Land-Use Planning and Zoning

reduce risk at community level by _______ public policy to direct how land is used through ____

Construction Standards and Building Codes

enforced at local level, that prescribes practices and measures that directly address known causes of disaster damages

Acquisition and Relocation

When land is not suitable for development/agricultural activity, that land can be acquired and placed into public use for environmental or recreational purposes.

Insurance

compensates affected parties for there losses

1. Rainwater Collection

2. Rainwater Catchment

3. Roof Water Collection

4. Rooftop Water Collection

Rainwater Harvesting is also called (4)

Rainwater Harvesting

practice of collecting and storing rain for later use

gutters - downspouts - storage vessels (simple barrels to large cistern) - surface runoff harvesting

From a roof to ...

catchment area x monthly rainfall x conversion factor x collection factor

ft2 x in x 0.623 x 75%-90%

= gallons per month

formula for minimum gallons you collect from rain water

1. source of water

2. total control over the water supply

3. reduce stormwater runoff and prevent water pollution

4. simple, inexpensive, and easy to maintain

5. flexible and modular

6. environmental benefits

Benefits of Rainwater Collection

law of diminishing returns

The phenomenon is known as the

Greywater Recycling

recycling household waste water that is not from toilet and can be used for toilet flushing, garden or lawn watering, or for crops

Potable Water System

most complex and expensive that can make home or building self-sufficient in terms of water supply

Un-gated outfalls

pipes and drains passing through levees that don't have gates; drain areas that are higher than the levee, such as higher ground and roof drains from nearby buildings.

Floodgates

prevent river water from backing through the sewer into the cities; open to let river water into the drain

Retention Structures

retain very acid water to prevent it from flowing into the river; impede fish from moving upstream, so only used where there is significant benefit

Tidal Gate

floodgate with a floating arm opens the gate and allows water exchange with each tide (adjustable to stop inflow at desired water level)

• automatic

• might be jammed open

Sluice Gates

most common gate, remain open most of the time, mounted in concrete gate chambers or manholes

with a sliding plate cover that can be opened to varying degrees

• simple, low cost and maintenance

• manual open and close

Winch Gates

gate using cable mechanism for horizontal or vertical opening (worm drive mechanism)

• rapid amount of water inflow and outflow

• manual, great risk of overtopping or closing difficulties

Flap Gates

at the end of small storm drains, usually round, hang from top hinge and remain closed except when pushed open by flowing water in the drain pipe, hydrostatic pressure seals the gate

• automatic

Flex Valve

replaced/more dependable than flap and sluice gates

rubber valves are mounted on the end of the storm outfall pipe, flex open to allow water from pipes but close under pressure of water against the outside of valve

• automatic

Weirs / Fixed Sill

a retention structure that partially block water in the drain with various designs and materials available (sandbags, rock/fill, concrete, steel)

Penstocks

a sluice floodgate or vertical lift gate placed on the landward side of a culvert for regulating the flow of a body of water.

Dropboard Culvert

simple design consisting of boards placed in slots in front of any culvert on the landward side

Surface Storage Basins

common method for managing stormwater

Surface Storage Basins

provide flow control through attenuation of storm water runoff, and releasing it slowly once the risk of flooding has passed

Surface Storage Basins

Important for storing and slowing stormwater runoff from nearby areas, especially areas with asphalt or concrete development because it flows much faster from these surfaces than naturally occurring areas and needs to be diverted to ensure the runoff occurs at the desired rate. The amount of cleaning and treatment of the water is limited.

Detention/Dry Ponds/Basins and Retention/Wet Ponds/Basins

2 Main Types of Surface Storage Basins

Detention/Dry Ponds/Basins

1. no permanent pool of water, orifice at the bottom, remains dry

2. no water quality benefits (concrete block to slow water flow and collect extra debris)

3. water is diverted due to very small slope

4. The inlet needs to be not more than 15% of the outlet

5. can be used as a public open space and recreational

6. mosquito breeding ground

7. vegetation to withstand dry or wet conditions

8. detract property value

9. cost less because of the generally smaller size

Retention/Wet Ponds/Basins

1. permanent pool of water, riser, and orifice at a higher point, looks like a regular pond

2. water quality benefits - can treat water (except when poorly designed)

3. water is diverted through a network of underground pipes

4. allows a large amount of water and the outlet lets a small amount of water

5. can be used as the habitat for aquatic species and recreational

6. mosquito breeding ground and drowning

7. vegetation for bank stability and aesthetic

8. add property value

9. simple and naturally processed water without additional equipment

Difference of the 2 Main Types of Surface Storage Basins

Pumps

Transfer fluids (gas or liquid) from one area to another by applying mechanical action

Pumps

Convert electrical energy into hydraulic energy.

Pumps

Driven by different power sources such as wind power, solar power, engine, or manual operation.

Hydraulic Pump

when require high hydraulic pressure. Heavy equipment needs lower suction pressures and high discharge pressures

positive displacement pump (for viscous) and dynamic pump (centrifugal)

2 main types of pump

Positive Displacement Pump

use moving parts (such as gears, lobes, plungers, pistons, or rotors) to transfer the fluids. The moving parts of these pumps discharge the fluid from the pump housing and increase the hydraulic pressure at the same time.

Positive Displacement Pump

They operate by trapping a specific amount of liquid in the pump chamber through an inlet valve and expelling it via the discharge valve. These pumps don't need manual priming because they have self-priming ability.

Reciprocating Pump

These types of pumps use a plunger or piston or diaphragm to transfer the fluids by moving downward and upward inside the pump cylinder

Suction (inlet open, fill liquid) and Discharge Stroke (outlet open, pressurized liquid)

Reciprocating pumps pumps fluids in 2 strokes

Check Valve

used in reciprocating pumps to prevent backward flow of the liquid

Plunger Pumps

has a crosshead operated by a cam handle device. The capacity of this pump is adjusted by varying its speed or the number of strokes. You can change the stroke through the setting of the eccentric pin.

plunger pumps

This pump uses a plunger instead of a piston. They are driven by electric, hydraulic, pneumatic, or steam-powered drives. mostly used for applications such as descaling, oil hydraulics, cleaning, water irrigation, and transporting paints, chocolates, pastries, etc.

Diaphragm Pumps

versatile type of pump. It uses a combination of Teflon, thermoplastic, or reciprocating rubber, and work on the air displacement principle.

Diaphragm Pumps

this pump have the ability to handle a large number of liquids, including dry food powders, wastewater, additives, pharmaceuticals, and chemicals, and does not require any packing or seals (leakage-free applications)

Piston Pumps

simple and powerful device. It uses a piston instead of a plunger. It has a piston, a cylinder, a casing, and a series of control units.

used for applications such as withdrawing water from the well or depth of the earth, reliable pressure, water irrigation, oil & gas, and distribution systems for transporting paint, pastry, chocolate, etc

Rotary Pump

The rotor of the pump transfers the fluid by orbiting and rotatory movement; consists of housing, vane, cams, runner, inlet, and outlet ports

Rotary Lobe Pumps (parang fan)

rotor of this type of pump does not touch the housing during its working. The liquid sucks in from the suction valve to the cavity between the chamber wall and the lobes.

Screw Pumps (2+ screw na umiikot, driver and driven screws)

singular kind of positive displacement rotary pump in which the liquid flowing through the pump element is axial. It is a non-clog, large-capacity, atmospheric pressure device that can pump various wastes and solids from the original raw sewage.

Progressive Cavity Pumps (isa lang umiikot tas naka hulma sa loob)

These types of pumps are specially designed for the transportation of viscous and abrasive liquids with a high content of air, fibers, and solids. The rigid steel screw rotor spins and rotates in the elastomer stator.

Gear Pumps

use a series of gears to transfer the fluid.