Carrari Ranch Channel Assessment

Carrari Ranch is a proposed residential development located in an unincorporated are of San Bernardino County north of Rancho Cucamonga.  The project encompasses 342 acres of which 74 will be developed.   The developed area will consist of 110 single-family detached homes, the remaining 268 acres will remain undeveloped, in its existing condition, and provide trail access to the surrounding Cucamonga Wilderness.

In the planning phase of the Carrari Ranch development PACE was tasked to provide a detailed hydraulic analysis of the project area.  An integral part of the the hydraulic analysis is the creation of a hydraulic model.  One of the factors used in the creation of the hydraulic model is the stream channel and floodplain roughness coefficient.  This factor is commonly referred to as the Manning’s n value and serves to represent the resistance of water flow over a surface.  The best way to obtain accurate values for the roughness coefficient that exists in the project area is to collect data for the conditions that actually exist in the field.  To accomplish this task PACE sent engineers into the field with a GPS enabled camera to document the texture of the soils and types and size of vegetation.  The pictures captured in the field observations are compared to well documented samples that have Manning’s n values assigned.  The GPS enabled camera allows PACE to document the locations of the field observations which allows us to create a more accurate hydraulic model based on ground conditions.