#block-header {
background: Red;
min-height: 100px;
-webkit-clip-path: url(#myClip);
clip-path: url(#myClip);
}
<h1>SVG image</h1>
<svg xmlns="http://www.w3.org/2000/svg" width="100%" height="100" viewBox="0 0 1 1" preserveAspectRatio="none"><path d="M0,0 1,0 1,0.9 C 1,0.9, 0.77,1, 0.5,1 0.23,1, 0,0.9,0,0.9z"/></svg>
<h1><code>clip-path</code> using the same SVG</h1>
<header id="block-header">
<svg width="0" height="0">
<defs>
<clipPath id="myClip" clipPathUnits="objectBoundingBox">
<path d="M0,0 1,0 1,0.9 C 1,0.9, 0.77,1, 0.5,1 0.23,1, 0,0.9,0,0.9z"/>
</clipPath>
</defs>
</svg>
</header>