  Solar flares release an enormous amount of energy into the corona. A
substantial fraction of this energy is transported to the lower atmosphere,
which results in chromospheric heating. The mechanisms that transport energy to
the lower solar atmosphere during a flare are still not fully understood. We
aim to estimate the temporal evolution of the radiative losses in the
chromosphere at the footpoints of a C-class flare, in order to set
observational constraints on the electron beam parameters of a RADYN flare
simulation. We estimated the radiative losses from hydrogen, and singly ionized
Ca and Mg using semi-empirical model atmospheres. To estimate the integrated
radiative losses in the chromosphere the net cooling rates were integrated
between the temperature minimum and the height where the temperature reaches 10
kK. The stratification of the net cooling rate suggests that the Ca IR triplet
lines are responsible for most of the radiative losses in the flaring
atmosphere. During the flare peak time, the contribution from Ca II H & K and
Mg II h & k lines are strong and comparable to the Ca IR triplet ($\sim$32 kW
m$^{-2}$). Since our flare is a relatively weak event the chromosphere is not
heated above 11 kK, which in turn yields a subdued Ly{\alpha} contribution
($\sim$7 kW m$^{-2}$). The temporal evolution of total integrated radiative
losses exhibits sharply-rising losses (0.4 kW m$^{-2}$ s$^{-1}$) and a
relatively slow decay (0.23 kW~m$^{-2}$ s$^{-1}$). The maximum value of total
radiative losses is reached around the flare peak time, and can go up to 175 kW
m$^{-2}$ for a single pixel located at footpoint. After a small parameter
study, we find the best model-data consistency in terms of the amplitude of
radiative losses and the overall atmospheric structure with a RADYN flare
simulation in the injected energy flux of $5\times10^{10}$ erg s$^{-1}$
cm$^{-2}$.
