Volume 2-05, Chapter 3 - City of Wichita

Section 3.2.5 - Enhanced Swale
D. PRETREATMENT / INLETS
• Inlets to enhanced swales must be provided with energy dissipaters such as riprap.
• A forebay or equivalent upstream pretreatment (sized at 0.1 acre-inch of volume per
impervious acre of contributing drainage area) shall be provided at the upstream end of
the facility to capture the larger particles. The forebay volume may be counted as part of
the WQ v .
• Enhanced swale systems that receive direct concentrated runoff may have a 6-inch drop
to a gravel diaphragm flow spreader at the upstream end of the control to help spread the
inflow.
• A gravel diaphragm and gentle side slopes may be provided along the top of channels to
provide pretreatment for lateral sheet flows.
E. OUTLET STRUCTURES
• The underdrain system should discharge to the storm drainage infrastructure or a stable
outfall.
F. EMERGENCY SPILLWAY
• Enhanced swales must be adequately designed to safely pass flows that exceed the
design storm flows.
G. MAINTENANCE ACCESS
• The local jurisdiction may require that the facility be placed in a reserve and/or
establishment of a drainage easement to the entire length of the facility, which is
accessible from a public road or other accessible easement. When required, the drainage
easement should be at least 20 feet wide, provide a minimum traversable width of 15 feet,
have a maximum slope of no more than 10%, and be appropriately stabilized to withstand
maintenance equipment and vehicles.
H. SAFETY FEATURES
• Ponding depths should be limited to a maximum of 18 inches.
I. LANDSCAPING
• Landscape design should specify proper grass species based on specific site and soils
conditions present along the channel.
J. ADDITIONAL SITE-SPECIFIC DESIGN CRITERIA AND ISSUES
Physiographic Factors - Local terrain design constraints
Low Relief: Reduced need for use of check dams.
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Volume 2, Technical Guidance