Introducing Geomorphic Engineering into Standard Stormwater Designs in the Kansas City Metro Area

Abstract

The Kansas City metro area is incorporating stream mechanics into its stormwater design standards. Here as in other urban areas, streams have degraded with the rapidly changing hydrology of the urban landscape. Streams disappear, incise, widen, meander or aggrade as the rate of delivery of water and sediment radically changes. The standard response in Kansas City metro as in much of the country is hard armor or channelization in an effort to maintain flood conveyance and control erosion. The hydraulic skills necessary are well established in the civil engineering community. However, the geomorphologic knowledge necessary to manage sustainable urban streams is not. In their 1999 report (FEMA, 1999) to Congress, the Federal Emergency Management Agency identified the shortage of professionals with expertise in fluvial process as a barrier to better stream management. Cities cannot fail to protect infrastructure or respond to citizen’s complaints while local designers try to learn a new discipline. The Kansas City metropolitan area addressed the knowledge gap through a set of design standards requiring a more complete analysis of stream condition. The region is promoting a better understanding of stream mechanics while solving the most common infrastructure and water quality problems. This approach explicitly acknowledges that there are a set of tasks customarily assigned to engineers specializing in infrastructure design rather than stream mechanics. Standard site development, pipeline crossings, outfalls, bridges and culverts in most urban areas are the province of the general civil engineer. However, by their very number, these types of stream interventions are responsible for much of the damage to urban stream stability. To remedy this problem, fluvial process must be translated into language familiar to and applicable by the general civil practitioner. The Mid-America Regional Council (MARC )and the Kansas City Metropolitan Chapter of the American Public Works Association (KC APWA) took up the task of Copyright ASCE 2004 World Water Congress 2004 2 developing new Standards Documents for adoption by area governments. For the first time, the stormwater design standards included a section on management of natural streams and riparian corridors . Specialists in urban fluvial geomorphology and hydraulics collaborated with a team of public works engineers to craft standards for required data, calculations and permissible design limits. Major departures from previous standards include required protection of the riparian corridor, elimination of the requirement to pipe headwaters streams and the addition of requirements to maintain sediment transport, avoid over-widening and provide for energy management throughout the project reach. This paper presents the results of that effort. The standards themselves are contained in Chapter 5605 of Section 5600, Storm Drainage Systems & Facilities, which can be downloaded from www.kcapwa.net/specifications.asp (Kansas City Metropolitan Chapter of the American Public Works Association, 2003).