Historical accounts of battles sometimes talk of rivers running red with the blood of fallen combatants.
Many Lancastrians were killed while fleeing; some trampled each other and others drowned in the rivers, which are said to have made them run red with blood for several days. (Wikipedia)
The ensuing massacre of the Parliamentarians is said to have been of such magnitude that the beck ran crimson with blood. (Wikipedia)
This seems implausible, given that a river’s water is flowing, therefore clearing the water of blood eventually. But, it would make a good scene in my story. What is the minimum plausible number of dead bodies it takes to cause a river to be stained in red for days?
- Technology is early medieval, so arrows, stab wounds, and drowning are primary causes of death.
- The river is medium-size: large enough to drown people but small enough to have people try to flee over it, similar to the Namsen River, in Norway at GPS (64.4464433N,11.8602026E). It is only 130 m across, meriting (failed) attempts by the wounded to swim to safety.
- The definition of "stained red" is that the water is a solid reddish hue when looked at from above.
- The stain must last for at least twenty-four hours, over at least a 1km stretch of the river.
- The river's water color is blue or blue-greenish most of the time.
Other cool numbers:
- 5 L of blood per person (estimate, usually between 4.7 and 5.7 L)
- The river speed is about 4-5 mph
- Blood density is 1060 kg/m³, so it will sink to the bottom eventually.