Diagram of a possible flood control plan in the plain of Troy

In the following diagram, yellow lines outline unnatural piles, the red arrows represent the direction flood waters are diverted.  Pooling water is represented by blue circles. Pilings channel the water, pools deepen as the storm continues. The general idea of flood control is to break up, slow down and/or channel the water toward its least harmful destination. The least harmful channel in the plain of Troy is the channel on the west side of the city. 

The system seems to be built to protect the city in the plain from floods by slowing and channeling water.  It has occurred to me that the south west side of the tell might contain a sea wall, or flood wall.  So, perhaps something like this.  

“When the rain, beginning in Mount Ida, extends to the plain, the wide and deep bed of the Menderé is completely filled; in a half or a quarter of an hour it rushes over its banks on both sides; on the left side it fills the swamps below Bunarbashi, while the Kirk Jos sends off a stream in the direction of its ancient bed to join the Menderé farther down. On the right it covers the high part of the plain over to the Kalifat Asmak, and transforms that stream into an impetuous river . If the rain continues a few hours, it often happens that the inundation prevails over the whole plain from the Hellespont to the springs at Bunarbashi. It happens also that about the season of the heaviest rains, the strong south-west winds blow, checking the current of the Hellespont, and raising the level of its waters, while these again impede the discharge of the rivers, and increase the inundation in the lower part of the plain.” 

(Peter Forschhammer, cited by Charles Maclaren, 1863 p. 62f )   

Forschhammer is talking about rain beginning in Ida.  But rain starts in the clouds.  He is thinking of two different phenomena.  One of them is a flash flood coming down the Scamander/Karamendere in the middle of the plain, which is caused by rains that never fell in the plain of Troy.  The water from such rains can reach the plain via the river, which originates on Ida.  

His second thought is a flash flood caused by rains in the plain (and elsewhere).  When the rain is hard and extended enough, the whole plain begins to move. Imagine ankle deep water from side to side in the plain. Then imagine knee deep water from side to side.  Now waist deep.  You get the picture.  

The city in the plain survived hundreds of floods.  It may have been destroyed in the end by a big flood, but it survived an annual flood and several flash floods every year of its existence.