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ch_rthsed.f90
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ch_rthsed.f90
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subroutine ch_rthsed
!! ~ ~ ~ PURPOSE ~ ~ ~
!! this subroutine routes sediment from subbasin to basin outlets
!! on a sub-daily timestep
!! ~ ~ ~ INCOMING VARIABLES ~ ~ ~
!! name |units |definition
!! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
!! |1 no vegetative cover on channel
!! ch_d(:) |m |average depth of main channel
!! ch_li(:) |km |initial length of main channel
!! ch_n(2,:) |none |Manning"s "n" value for the main channel
!! ch_s(2,:) |m/m |average slope of main channel
!! ch_si(:) |m/m |initial slope of main channel
!! ch_wdr(:) |m/m |channel width to depth ratio
!! hdepth(:) |m |depth of flow on day
!! hhstor(:) |m^3 H2O |water stored in reach at end of time step
!! hrtwtr(:) |m^3 H2O |water leaving reach during time step
!! hsdti(:) |m^3/s |average flow rate during time step
!! rhy(:) |m H2O |main channel hydraulic radius
!! sedst(:) |metric tons |amount of sediment stored in reach
!! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
!! ~ ~ ~ OUTGOING VARIABLES ~ ~ ~
!! name |units |definition
!! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
!! ch_d(:) |m |average depth of main channel
!! ch_s(2,:) |m/m |average slope of main channel
!! peakr |m^3/s |peak runoff rate in channel
!! sedst(:) |metric tons |amount of sediment stored in reach
!! sedrch |metric tons |sediment transported out of channel on day
!! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
!! ~ ~ ~ LOCAL DEFINITIONS ~ ~ ~
!! name |units |definition
!! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
!! dat2 |m |change in channel depth during time step
!! deg |metric tons |sediment reentrained in water by channel degradation
!! dep |metric tons |sediment deposited on river bottom
!! depdeg |m |depth of degradation/deposition from original
!! depnet |metric tons |
!! dot |
!! ii |none |counter
!! jrch |none |reach number
!! qin |m^3 H2O |water in reach during time step
!! vc |m/s |flow velocity in reach
!! sedcon |mg/L |sediment concentration
!! shrstrss |none |critical shear stress for bed erosion
!! Reynolds_g |none |grain Reynolds number
!! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
!! ~ ~ ~ SUBROUTINES/FUNCTIONS CALLED ~ ~ ~
!! Intrinsic: Max
!! SWAT: ttcoef
!! code modified by J.Jeong and N.Kannan for urban sub-hourly sediment modeling
!! and by Balagi for bank erosion.
!! Brownlie (1981) bed load model and Yang (1973, 1984) model added.
!! ~ ~ ~ ~ ~ ~ END SPECIFICATIONS ~ ~ ~ ~ ~ ~
use basin_module
use channel_data_module
use time_module
use channel_module
use hydrograph_module, only : ob
use climate_module
implicit none
integer :: ii !none |counter
integer :: icmd !units |description
integer :: jrch !none |reach number
integer :: iwst !none |counter
real :: qin !m^3 H2O |water in reach during time step
real :: qdin !m^3 H2O |water in reach during time step
real :: sedin !units |description
real :: vc !m/s |flow velocity in reach
real :: cyin !units |description
real :: cych !units |description
real :: depnet !metric tons |
real :: deg !metric tons |sediment reentrained in water by channel degradation
real :: dep !metric tons |sediment deposited on river bottom
real :: depdeg !m |depth of degradation/deposition from original
real :: dot !mm |actual depth from impermeable layer to water level
! |above drain during subsurface irrigation
real :: ycoeff !units |description
real :: Reynolds_g !none |grain Reynolds number
real :: visco_h2o !units |description
real :: tmpw !units |description
real :: channel_d50 !units |description
real :: particle_specific_gravity !units |description
real :: Fr_g !units |description
real :: Fr_gc !units |description
real :: log10sedcon !units |description
real :: sedcon !g/m^3 |sediment concentration
real :: deg24 !units |description
real :: dep24 !units |description
real :: vfall !units |description
real :: coefa !units |description
real :: coefb !units |description
real :: coefc !units |description
real :: coefd !units |description
real :: coefe !units |description
real :: thbase !units |description
real :: shear_stress !units |description
real :: vshear !units |description
real :: deg1 !units |description
real :: deg2 !units |description
real :: d_fract !units |description
real :: dat2 !m |change in channel depth during time step
deg24=0.; dep24=0
channel_d50 = bsn_prm%ch_d50 / 1000. !! unit change mm->m
particle_specific_gravity = 2.65
sedin = 0.
do ii = 1, time%step
if (hrtwtr(ii)>0. .and. hdepth(ii)>0.) then
!! initialize water in reach during time step
qin = 0.
sedin = 0.
qin = hrtwtr(ii) + hhstor(ii)
!! do not perform sediment routing if no water in reach
if (qin > 0.01) then
!! initialize sediment in reach during time step
if (ii == 1) then
sedin = ob(icmd)%ts(1,ii)%sed + ch(jrch)%sedst
else
sedin = ob(icmd)%ts(1,ii)%sed + hsedst(ii-1)
end if
if (sedin < 1.e-6) sedin = 0.
!! initialize reach peak runoff rate
peakr = hsdti(ii)
!! calculate flow velocity
vc = 0.
if (hharea(ii) < .010) then
vc = 0.01
else
vc = peakr / hharea(ii)
end if
if (vc > 5.) vc = 5.
thbase = 0.
thbase = ch_hyd(jhyd)%l * 1000. / (3600. * 24. * vc)
if (thbase > 1.) thbase = 1.
!! JIMMY"S NEW IMPROVED METHOD for sediment transport
cyin = 0.
cych = 0.
depnet = 0.
deg = 0.
dep = 0.
if (sedin < 1e-6) sedin = 0.
cyin = sedin / qin !tons/m3
!!water temperature (Celsius)
tmpw = 5.0 + 0.75 * wst(iwst)%weat%tave
!! water viscosity (m2/s) using 3rd order polynomial interpolation
visco_h2o = -3.e-6 * tmpw ** 3 + 0.0006 * tmpw ** 2 - &
0.0469 * tmpw + 1.7517
visco_h2o = visco_h2o * 1.e-6
!! Use either Brownlie or Yang Model for bead load calculation
select case (bsn_cc%sed_ch)
case (0)
!! Bagnold"s (1977) stream power
cych = bsn_prm%spcon * vc ** bsn_prm%spexp
case (1)
!!Brownlie Model
!! grain Reynolds number
Reynolds_g = sqrt(9.81 * channel_d50 ** 3) / visco_h2o
!!critical shear stress for grain Froude number
ycoeff = (sqrt(particle_specific_gravity - 1.) * &
Reynolds_g) ** (-0.6)
shear_stress = 0.22 * ycoeff + 0.06 * 10 ** (-7.7 * ycoeff)
!! critical grain Froude number
fr_gc = 4.596 * shear_stress ** 0.5293 * ch_hyd(jhyd)%s ** &
(-0.1405) * 1.57 ** (-0.1606)
!! grain Froude number
fr_g = vc / sqrt((particle_specific_gravity - 1.) * &
9.81 * (bsn_prm%ch_d50 / 1000.))
!! sediment concentration at the channel outlet [ppm, or g/m3]
if(fr_g>fr_gc) then
sedcon = 7115 * 1.268 * (fr_g - fr_gc) ** 1.978 * &
ch_hyd(jhyd)%s ** 0.6601 * (rhy(ii) / &
channel_d50) ** (-0.3301)
else
sedcon = 0.
endif
cych = sedcon * 1.e-6 !tons/m3
case (2)
!!Yang Model
!! particle fall velocity
vfall = 9.81 * channel_d50 ** 2 * (particle_specific_gravity - 1.) &
/ (18.* visco_h2o)
!! shear velocity
vshear = sqrt(9.81 * rhy(ii) * ch_hyd(jhyd)%s)
coefa = vfall * channel_d50 / visco_h2o
coefe = vshear * channel_d50 / visco_h2o
if(coefe<70) then
if (coefe<1.2) coefe = 1.2
coefb = 2.5 / (log10(coefe) - 0.06) + 0.66
elseif(coefe>=70) then
coefb = 2.05
else
write(*,*) "Error in implementing Yang erosion model"
!! stop
endif
coefc = vshear / vfall
coefd = vc * ch_hyd(jhyd)%s / vfall - coefb * ch_hyd(jhyd)%s
if(coefd<=0) coefd = 1.e-6
if(bsn_prm%ch_d50 <= 2.0) then ! in millimeter
!! use sand equation (1973)
log10sedcon = 5.435 - 0.286 * log10(coefa) - 0.457 * &
log10(coefc) +(1.799 - 0.409 *log10(coefa) - 0.314 * &
log10(coefc)) * log10(coefd)
elseif (bsn_prm%ch_d50 > 2.0) then
!! use gravel equation (1984)
log10sedcon = 6.681 - 0.633 * log10(coefa) - 4.816 * &
log10(coefc) +(2.784 - 0.305 *log10(coefa) - 0.282 * &
log10(coefc)) * log10(coefd)
endif
sedcon = 10 ** log10sedcon !ppm
cych = sedcon * 1.e-6 !tons/m3
end select
depnet = qin * (cych - cyin)
if(abs(depnet) < 1.e-6) depnet = 0.
!! tbase is multiplied so that erosion is proportional to the traveltime,
!! which is directly related to the length of the channel
!! Otherwise for the same discharge rate and sediment deficit
!! the model will erode more sediment per unit length of channel
!! from a small channel than a larger channel. Modification made by Balaji Narasimhan
if (depnet > 1.e-6) then
deg = depnet * thbase
!! First the deposited material will be degraded before channel bed
if (deg >= ch(jrch)%depch) then
deg1 = ch(jrch)%depch
deg2 = (deg - deg1) * ch_sed(jsed)%cov1*ch_sed(jsed)%cov2
ch(jrch)%depch = 0.
else
deg1 = deg
deg2 = 0.
ch(jrch)%depch = ch(jrch)%depch- deg1
endif
dep = 0.
else
dep = -depnet * thbase
deg = 0.
deg1 = 0.
deg2 = 0.
endif
hsedyld(ii) = sedin + deg1 + deg2 - dep
if (hsedyld(ii) < 1.e-12) hsedyld(ii) = 0.
d_fract = hrtwtr(ii) / qin
if (d_fract > 1.) d_fract = 1.
hsedyld(ii) = hsedyld(ii) * d_fract
!! In this default sediment routing sediment is not tracked by particle size
rch_san = 0.
rch_sil = rch_sil + hsedyld(ii) !All are assumed to silt part
rch_cla = 0.
rch_sag = 0.
rch_lag = 0.
rch_gra = 0.
hsedst(ii) = sedin + deg1 + deg2 - dep - hsedyld(ii)
if (hsedst(ii) < 1.e-12) hsedst(ii) = 0.
ch(jrch)%depch = ch(jrch)%depch + dep
ch(jrch)%sedst = hsedst(ii)
deg24 = deg24 + deg2
dep24 = dep24 + dep
else
hsedst(ii) = sedin
ch(jrch)%sedst = hsedst(ii)
end if
end if
end do
!! Organic nitrogen and Organic Phosphorus contribution from channel erosion
ch(jrch)%orgn = deg24 * ch_nut(jnut)%onco * 1000.
ch(jrch)%orgp = deg24 * ch_nut(jnut)%opco * 1000.
qdin = 0.
qdin = rtwtr + ch(jrch)%rchstor
if ((rtwtr == 0. .and. rchdep == 0.) .or. qdin <= 0.01) then
sedrch = 0.
rch_san = 0.
rch_sil = 0.
rch_cla = 0.
rch_sag = 0.
rch_lag = 0.
rch_gra = 0.
end if
!! compute changes in channel dimensions
if ((rtwtr > 0. .and. rchdep > 0.) .or. qdin > 0.01) then
if (bsn_cc%deg == 1) then
qdin = 0.
qdin = rtwtr + ch(jrch)%rchstor
depdeg = 0.
depdeg = ch_hyd(jhyd)%d - ch(jrch)%di
if (depdeg < ch(jrch)%si * ch(jrch)%li * 1000.) then
if (qdin > 1400000.) then
dot = 0.
dot = 358.6 * rchdep * ch_hyd(jhyd)%s * ch_sed(jsed)%cov1
dat2 = 1.
dat2 = dat2 * dot
ch_hyd(jhyd)%d = ch_hyd(jhyd)%d + dat2
ch_hyd(jhyd)%w = ch_hyd(jhyd)%wdr * ch_hyd(jhyd)%d
ch_hyd(jhyd)%s = ch_hyd(jhyd)%s - dat2 / (ch_hyd(jhyd)%l &
* 1000.)
ch_hyd(jhyd)%s = Max(.0001, ch_hyd(jhyd)%s)
call ch_ttcoef(jrch)
endif
endif
endif
endif
return
end subroutine ch_rthsed