flow accumulation lines not connected

[teakplantation]

While trying to create a watershed area, I run into the following problem. 

I calculated flow direction & flow accumulation along a topography with clear valleys (red arrows in picture below, with contour lines at 1 m distance spacing and raster at 1x1m resolution). 

Why are my flow lines stopping on the way downhill instead of merging into one larger flow line?

[DanPatterson · Accepted solution]

Did you fill depressions to create a proper surface for flow accumuation?

Fill (Spatial Analyst)—ArcGIS Pro | Documentation

Creating a depressionless DEM—ArcGIS Pro | Documentation

generally fill your sinks, determine flow direction then flow accumulation

[teakplantation]

Thanks Dan, spot on!