html, body { height: 100% }
#map { min-height: 100%; }
body {
    margin: 0;
    font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 12px;
    overflow: hidden;
    background-color: #f00;
}
.leaflet-popup-content-wrapper {
    -webkit-border-radius: 5px;
    border-radius: 5px;
}

path.river          { /*stroke: #29439c;*/stroke-linejoin:round;stroke-linecap:round;fill:none; }
path.highlightriver {stroke: yellow !important; }

#headerbar {
  position:         fixed;
  width:            50%;
  left:             50%;
  height:           2em;
  font-size:        1.5em;
  padding-top:      0.5em;
  background-color: rgba(0,0,255,0.5);
  text-align:       center;
}
html, body { height: 100% }
#map { min-height: 100%; }
body {
    margin: 0;
    font-family: Helvetica Neue, Helvetica, Arial, sans-serif; font-size: 12px;
    overflow: hidden;
    background-color: #f00;
}
.leaflet-popup-content-wrapper {
    -webkit-border-radius: 5px;
    border-radius: 5px;
}

path.river          { /*stroke: #29439c;*/stroke-linejoin:round;stroke-linecap:round;fill:none; }
path.highlightriver {stroke: yellow !important; }

#headerbar {
  position:         fixed;
  width:            50%;
  left:             25%;
  height:           2em;
  font-size:        1.5em;
  padding-top:      0.5em;
  background-color: rgba(0,0,255,0.5);
  text-align:       center;
}
Adjust left of header bar
Adjust left of header bar
