climate change on UAE - Stockholm Environment Institute-US Center

ut it is definitely better to use high-resolution
maps like cartographic maps at 1:25,000 or
smaller to improve accuracy (Jarvis et al., n.d.).
Other authors point out that coarser resolution
DEMs ignore details of surface characteristics
like steep slopes (Dong et al., n.d.) and because
the values are often represented as integers (at
least in USGS DEMs), modeled slope for areas
of limited reliefs would even show “artificial
jumps” in slopes over shorter distances
(Hodgson et al., 2003; Carter, 1992).
Cho and Lee (2001) and Dong et al. (n.d.)
confirm the emphasis in Jarvis et al. (n.d.)
with respect to the influence of DEM accuracy
on hydrological models. Cho and Lee’s paper
exploring sensitivity considerations found
that with a 1:24,000 DEM (7.5 minute), their
hydrologic model revealed higher runoff volumes
which the 1:250,000 (1 degree) DEM flattens the
watershed’s slope yielding delayed stream flow
and underestimating runoff and erosion. The
two credited the finer resolution of 7.5-minute
dataset, with yielding increased average slope
and thus higher runoff when the simulation was
run. Dong et al., (n.d.), in their comparison of
Synthetic Aperture Radar (InSAR), LiDAR,
and photogrammetrically derived DEMs (Noble
et al., n.d.), similarly found that the main
differences in topographic attributes revealed
during their research were in river channels,
having implications for hydrological processes.
Their paper highlights importance of accurate
terrain modeling on hydrologic simulations on
the Broadhead watershed in New Jersey; their
conclusions can extend to coastal flood plains
and would affect storm surge and sea level rise
modeling.
Conclusion
Elevation of coastal land is a critical factor in
determining its vulnerability to sea level rise, a
key impact of <strong>climate</strong> <strong>change</strong> on coastal areas.
Most sea level rise (SLR) scenarios estimate
50-100cm inundation over the next century
depending on the region. In modeling sea level
rise based on elevation, following components
of a DEM are in question.
Data source and method of collection
Vertical and horizontal resolution
Aspect
Slope
Terrain is another important determinant of
DEM accuracy, particularly for DEMs derived
from SRTM and LiDAR data. Jarvis et al. (n.d.)
found that SRTM overestimates for northeast
facing slopes and underestimates for southwest
facing slopes (correlating with flight path
directions). Others highlighted the challenge of
modeling areas of limited relief using elevation
intervals of 1 meter, or even 10-50 meter jumps
as many do, and the inappropriateness of such
data for limited relief coastal areas vulnerable
to sea level rise.
The challenge, to date, as we noted in the body
of the report has been estimating vulnerable
zones based on these