TY - CONF
T1 - Controls on delta formation, area, and topset slope: New predictive relationships developed using a global delta dataset
AU - Caldwell, R. L.
AU - Edmonds, D. A.
AU - Baumgardner, S. E.
AU - Paola, C.
AU - Roy, S.
AU - Nienhuis, J.
N1 - American Geophysical Union, Fall Meeting 2017, abstract #EP14B-08
PY - 2017/12/1
Y1 - 2017/12/1
N2 - River deltas are irreplaceable natural and societal resources, though
they are at risk of drowning due to sea-level rise and decreased
sediment delivery. To enhance hazard mitigation efforts in the face of
global environmental change, we must understand the controls on delta
growth. Previous empirical studies of delta growth are based on small
datasets and often biased towards large, river-dominated deltas. We are
currently lacking relationships that predict delta formation, area, or
topset slope across the full breadth of global deltas. To this end, we
developed a global dataset of 5,229 rivers (with and without deltas)
paired with nine upstream (e.g., sediment discharge) and four downstream
(e.g., wave height) environmental variables. Using Google Earth imagery,
we identify all coastal river mouths (≥ 50 m wide) connected to an
upstream catchment, and define deltas as river mouths that split into
two or more distributary channels, end in a depositional protrusion from
the shoreline, or do both. Delta area is defined as the area of the
polygon connecting the delta node, two lateral shoreline extent points,
and the basinward-most extent of the delta. Topset slope is calculated
as the average, linear slope from the delta node elevation (extracted
from SRTM data) to the main channel mouth, and shoreline and basinward
extent points. Of the 5,229 rivers in our dataset, 1,816 (35%) have a
delta. Using 495 rivers (those with data available for all variables),
we build an empirically-derived relationship that predicts delta
formation with 76% success. Delta formation is controlled predominantly
by upstream water and sediment discharge, with secondary control by
downstream waves and tides that suppress delta formation. For those
rivers that do form deltas, we show that delta area is best predicted by
sediment discharge, bathymetric slope, and drainage basin area (R2 =
0.95, n = 170), and exhibits a negative power-law relationship with
topset slope (R2 = 0.85, n = 1,342). Topset slope is best predicted by
grain size and wave height (R2 = 0.50, n = 358). These empirical
relationships can aid in forecasting delta response to continued global
environmental change.
AB - River deltas are irreplaceable natural and societal resources, though
they are at risk of drowning due to sea-level rise and decreased
sediment delivery. To enhance hazard mitigation efforts in the face of
global environmental change, we must understand the controls on delta
growth. Previous empirical studies of delta growth are based on small
datasets and often biased towards large, river-dominated deltas. We are
currently lacking relationships that predict delta formation, area, or
topset slope across the full breadth of global deltas. To this end, we
developed a global dataset of 5,229 rivers (with and without deltas)
paired with nine upstream (e.g., sediment discharge) and four downstream
(e.g., wave height) environmental variables. Using Google Earth imagery,
we identify all coastal river mouths (≥ 50 m wide) connected to an
upstream catchment, and define deltas as river mouths that split into
two or more distributary channels, end in a depositional protrusion from
the shoreline, or do both. Delta area is defined as the area of the
polygon connecting the delta node, two lateral shoreline extent points,
and the basinward-most extent of the delta. Topset slope is calculated
as the average, linear slope from the delta node elevation (extracted
from SRTM data) to the main channel mouth, and shoreline and basinward
extent points. Of the 5,229 rivers in our dataset, 1,816 (35%) have a
delta. Using 495 rivers (those with data available for all variables),
we build an empirically-derived relationship that predicts delta
formation with 76% success. Delta formation is controlled predominantly
by upstream water and sediment discharge, with secondary control by
downstream waves and tides that suppress delta formation. For those
rivers that do form deltas, we show that delta area is best predicted by
sediment discharge, bathymetric slope, and drainage basin area (R2 =
0.95, n = 170), and exhibits a negative power-law relationship with
topset slope (R2 = 0.85, n = 1,342). Topset slope is best predicted by
grain size and wave height (R2 = 0.50, n = 358). These empirical
relationships can aid in forecasting delta response to continued global
environmental change.
KW - 1825 Geomorphology: fluvial
KW - HYDROLOGY
KW - 1861 Sedimentation
KW - 4315 Monitoring
KW - forecasting
KW - prediction
KW - NATURAL HAZARDS
KW - 4235 Estuarine processes
KW - OCEANOGRAPHY: GENERAL
M3 - Abstract
ER -