Mass Wasting - Mitigation Flashcards
since when did mgb started hazard assessments
2013 after yolanda
hazard assessment under mgb
flood, landslide, ground subsidence/karst, coastal hazard assessments
regional and detailed scale maps
1:50000
1:10000
they are mandated to conduct studies related to rain-induced landslide
mgb
how does mgb conduct geohazard mapping
remote sensing
field assessment
anecdotal accounts
what do you look for during field assessment
tension cracks, depth of tension, vertical and horizontal displacement,
gently sloping areas with no identified landslides
low landslide susceptibility
areas with moderately steep slopes, soil creep and other indications of possible landslide occurrence are present
moderate landslide susceptibility
areas with steep to very steep slopes and underlain by weak materials. areas with numerous old/inactive landslides
high landslide susceptibility
areas with steep to very steep slopes and underlain by weak materials. recent landslides, escarpments and tension cracks are present. human initiated effects could be an aggravating factor
very high landslide susceptibility
areas that could be affected by landslide debris
debris flow/ possible accumulation zone
slope classification
0-3 : level to nearly level
3-8 : gently sloping to undulating
8-18 : undulating to rolling
18-30 : rolling to moderately steep
30-50 : steep
>50 : very steep
non structural mass wasting mitigation
- zoning laws
- construction ordinances
- geohazard assessment
- research and extension
- information dissemination
structural mass wasting mitigation
retaining walls
rock bolts
controlling water
terracing
covering steep slopes
reducing slope materials
protective structure
if the objective is to prevent movement, then slope stability can be maximized by simultaneously increasing _____ and decreasing _____
frictional forces
the weight acting downslope
commonly used whenever a flat or level surface is needed in sloping terrain
retaining walls
used to anchor loose rocks to more massive, solid bodies
rock bolts
control or limit the amount of water that can accumulate in the slope material
controlling water
controlling water involves installment of _____ and ____ which is not common on the Ph
perforated pipes
gravel beds
used to cover slope to prevent water from infiltrating
impervious plastic sheet
creating a series of benches on a hillside, decreasing steepness but breaks slope into shorter segments
terracing
is an ancient practice in parts of asia and south america where they provide flat areas for frowing food
terracing
involves covering bare slopes with new vegetation, crushed rocks, or synthetic mesh
covering steep slopes
t or f: it may be more expensive to actually remove a dangerous slope rather than try to stabilize it by physical means
FALSE (cost effective)
involves building of structures that keep material that is moving downslope from coming into contact with people or surroundngs
protective structures
large barriers in valleys to trap debris
trap
allow materials to safely move over transportation routes
shelter
buildings can be protected by constructing retaining walls that will diver material
diversion
how high are the river banks of Davao River?
5m
engineering controls are based on the
type off expected movement and the characteristics of the site itself
in some cases, landslide engineering control goal is to _______, in other, it is simply to ________
prevent movement ; provide protection from movement
used to reinforce both temporary and permanent excavations by spraying concrete
shotcreting
________ is important in keeping water from flowing into open fractures at the top of slides and slump
diverting water
t or f: the buildup of water in some slopes can be minimized by limiting the amount of water being used nearby for landscape or agricultural irrigation
T
terracing is common in
open pit/surface mining or in roadcuts
common way of establishing a blanket of grass is a technique called
hydroseeding
a slurry of seed and fertilizer is sprayed onto a bare slope
hydroseeding
t or f: hydroseeding is costly
T
